| 1. |
- Bergman, Marie-Louise, et al.
(författare)
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Diabetes protection and restoration of thymocyte apoptosis in NOD Idd6 congenic strains
- 2003
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 52:7, s. 1677-1682
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Tidskriftsartikel (refereegranskat)abstract
- Type 1 diabetes in the nonobese diabetic (NOD) mouse is a multifactorial and polygenic disease. The NOD-derived genetic factors that contribute to type 1 diabetes are named Idd (insulin-dependent diabetes) loci. To date, the biological functions of the majority of the Idd loci remain unknown. We have previously reported that resistance of NOD immature thymocytes to depletion by dexamethazone (Dxm) maps to the Idd6 locus. Herein, we refine this phenotype using a time-course experiment of apoptosis induction upon Dxm treatment. We confirm that the Idd6 region controls apoptosis resistance in immature thymocytes. Moreover, we establish reciprocal Idd6 congenic NOD and B6 strains to formally demonstrate that the Idd6 congenic region mediates restoration of the apoptosis resistance phenotype. Analysis of the Idd6 congenic strains indicates that a 3-cM chromosomal region located within the distal part of the Idd6 region controls apoptosis resistance in NOD immature thymocytes. Together, these data support the hypothesis that resistance to Dxm-induced apoptosis in NOD immature thymocytes is controlled by a genetic factor within the region that also contributes to type 1 diabetes pathogenesis. We propose that the diabetogenic effect of the Idd6 locus is exerted at the level of the thymic selection process.
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| 2. |
- Wendt, Anna, et al.
(författare)
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Glucose Inhibition of Glucagon Secretion From Rat alpha-Cells Is Mediated by GABA Released From Neighboring beta-Cells.
- 2004
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 53:4, s. 1038-1045
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Tidskriftsartikel (refereegranskat)abstract
- γ-Aminobutyric acid (GABA) has been proposed to function as a paracrine signaling molecule in islets of Langerhans. We have shown that rat β-cells release GABA by Ca2+-dependent exocytosis of synaptic-like microvesicles. Here we demonstrate that GABA thus released can diffuse over sufficient distances within the islet interstitium to activate GABAA receptors in neighboring cells. Confocal immunocytochemistry revealed the presence of GABAA receptors in glucagon-secreting α-cells but not in β- and δ-cells. RT-PCR analysis detected transcripts of α1 and α4 as well as β1–3 GABAA receptor subunits in purified α-cells but not in β-cells. In whole-cell voltage-clamp recordings, exogenous application of GABA activated Cl− currents in α-cells. The GABAA receptor antagonist SR95531 was used to investigate the effects of endogenous GABA (released from β-cells) on pancreatic islet hormone secretion. The antagonist increased glucagon secretion at 1 mmol/l glucose twofold and completely abolished the inhibitory action of 20 mmol/l glucose on glucagon release. Basal and glucose-stimulated secretion of insulin and somatostatin were unaffected by SR95531. The L-type Ca2+ channel blocker isradipine evoked a paradoxical stimulation of glucagon secretion. This effect was not observed in the presence of SR95531, and we therefore conclude that isradipine stimulates glucagon secretion by inhibition of GABA release.
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| 3. |
- Barg, Sebastian, et al.
(författare)
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A Subset of 50 Secretory Granules in Close Contact With L-Type Ca(2+) Channels Accounts for First-Phase Insulin Secretion in Mouse beta-Cells.
- 2002
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Ingår i: Diabetes. - 1939-327X .- 0012-1797. ; 51 Suppl 1, s. 74-82
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Tidskriftsartikel (refereegranskat)abstract
- Capacitance measurements were applied to mouse pancreatic beta-cells to elucidate the cellular mechanisms underlying biphasic insulin secretion. We report here that only <50 of the beta-cell's >10,000 granules are immediately available for release. The releasable granules tightly associate with the voltage-gated alpha(1C) Ca(2+) channels, and it is proposed that the release of these granules accounts for first-phase insulin secretion. Subsequent replenishment of the releasable pool by priming of previously nonreleasable granules is required for second-phase insulin secretion. The latter reaction depends on intragranular acidification due to the concerted action of granular bafilomycin-sensitive v-type H(+)-ATPase and 4,4-diisothiocyanostilbene-2,2-disulfonate--blockable ClC-3 Cl(-) channels. Lowering the cytoplasmic ATP/ADP ratio prevents granule acidification, granule priming, and refilling of the releasable pool. The latter finding provides an explanation to the transient nature of insulin secretion elicited by, for example, high extracellular K(+) in the absence of metabolizable fuels.
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| 4. |
- Barg, Sebastian, et al.
(författare)
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Tight coupling between electrical activity and exocytosis in mouse glucagon-secreting alpha-cells
- 2000
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Ingår i: Diabetes. - 1939-327X .- 0012-1797. ; 49:9, s. 1500-1510
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Tidskriftsartikel (refereegranskat)abstract
- alpha-Cells were identified in preparations of dispersed mouse islets by immunofluorescence microscopy. A high fraction of alpha-cells correlated with a small cell size measured as the average cell diameter (10 microm) and whole-cell capacitance (<4 pF). The alpha-cells generated action potentials at a low frequency (1 Hz) in the absence of glucose. These action potentials were reversibly inhibited by elevation of the glucose concentration to 20 mmol/l. The action potentials originated from a membrane potential more negative than -50 mV, had a maximal upstroke velocity of 5 V/s, and peaked at +1 mV. Voltage-clamp experiments revealed the ionic conductances underlying the generation of action potentials. alpha-Cells are equipped with a delayed tetraethyl-ammonium-blockable outward current (activating at voltages above -20 mV), a large tetrodotoxin-sensitive Na+ current (above -30 mV; peak current 200 pA at +10 mV), and a small Ca2+ current (above -50 mV; peak current 30 pA at +10 mV). The latter flowed through omega-conotoxin GVIA (25%)- and nifedipine-sensitive (50%) Ca(2+)-channels. Mouse alpha-cells contained, on average, 7,300 granules, which undergo Ca(2+)-induced exocytosis when the alpha-cell is depolarized. Three functional subsets of granules were identified, and the size of the immediately releasable pool was estimated as 80 granules, or 1% of the total granule number. The maximal rate of exocytosis (1.5 pF/s) was observed 21 ms after the onset of the voltage-clamp depolarization, which is precisely the duration of Ca(2+)-influx during an action potential. Our results suggest that the secretory machinery of the alpha-cell is optimized for maximal efficiency in the use of Ca2+ for exocytosis.
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| 5. |
- Borg, Henrik, et al.
(författare)
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A 12-year prospective study of the relationship between islet antibodies and beta-cell function at and after the diagnosis in patients with adult-onset diabetes.
- 2002
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 51:6, s. 1754-1762
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Tidskriftsartikel (refereegranskat)abstract
- To clarify the relationships between islet antibodies (islet cell antibody [ICA], GAD antibody [GADA], and IA-2 antibody [IA-2A]) versus the progression of beta-cell dysfunction, we have followed a group of diabetic patients from their diagnosis at 21-73 years of age. Patients with ICA had high levels of GADA and/or IA-2A at diagnosis and a more severe beta-cell dysfunction 5 years after diagnosis than those with only GADA in low concentrations. The aim of the current 12-year follow-up study was to examine the further progression of beta-cell dysfunction in relation to islet antibodies at and after diagnosis. Among 107 patients, complete beta-cell failure 12 years after diagnosis was restricted to those with islet antibodies at diagnosis (16 of 21 [77%] with multiple antibodies and 4 of 5 [80%] with only GADA). In contrast, among antibody-negative patients, fasting P-C-peptide levels were unchanged. Most GADA-positive patients (22 of 27 [81%]) remained GADA positive after 12 years. Associated with decreasing fasting P-C-peptide levels (0.85 nmol/l [0.84] at diagnosis vs. 0.51 nmol/l [0.21] 12 years after diagnosis, P < 0.05), ICA developed after diagnosis in 6 of 105 originally antibody negative mostly overweight patients. In conclusion, multiple islet antibodies or GADA alone at diagnosis of diabetes predict future complete beta-cell failure. After diagnosis, GADA persisted in most patients, whereas ICA development in patients who were antibody negative at diagnosis indicated decreasing beta-cell function.
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| 6. |
- Cervin, Camilla, et al.
(författare)
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Cosegregation of MIDD and MODY in a Pedigree: Functional and Clinical Consequences.
- 2004
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 53:7, s. 1894-1899
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was characterization of a family carrying two mutations known to cause monogenic forms of diabetes, the M626K mutation in the HNF1α gene (MODY3) and the A3243G in mtDNA. β-Cell function and insulin sensitivity were assessed with the Botnia clamp. Heteroplasmy of the A3243G mutation and variants in type 2 diabetes susceptibility genes were determined, and transcriptional activity, DNA binding, and subcellular localization of mutated HNF1α were studied. Thirteen family members carried the mutation in mtDNA; 6 of them also had the M626K mutation, whereas none had only the M626K mutation. The protective Ala12 allele in peroxisome proliferator–activated receptor (PPAR)γ was present in two nondiabetic individuals. Carriers of both mtDNA and HNF1α mutations showed an earlier age at onset of diabetes than carriers of only the mtDNA mutation (median 22 vs. 45 years) but no clear difference in β-cell function or insulin sensitivity. In vitro, the M626K mutation caused a 53% decrease in transcriptional activity in HeLa cells. The mutated protein showed normal nuclear targeting but increased DNA binding. These data demonstrate that several genetic factors might contribute to diabetes risk, even in families with mtDNA and HNF1α mutations.
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| 7. |
- Ek, I, et al.
(författare)
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A unique defect in the regulation of visceral fat cell lipolysis in the polycystic ovary syndrome as an early link to insulin resistance
- 2002
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 51:2, s. 484-492
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Tidskriftsartikel (refereegranskat)abstract
- The etiology of polycystic ovary syndrome (PCOS) is unknown. However, PCOS has a strong resemblance to the insulin resistance (metabolic) syndrome, where an increased rate of visceral fat cell lipolysis is believed to play a pathophysiological role. We hypothesized that primary defects in visceral lipolysis might also exist in PCOS. Ten young, nonobese, and otherwise healthy PCOS women were compared with 13 matched control women. In vitro lipolysis regulation and stoichiometric properties of the final step in lipolysis activation, namely the protein kinase A (PKA)-hormone sensitive lipase (HSL) complex, were investigated in isolated visceral (i.e., omental) fat cells. Body fat distribution and circulating levels of insulin, glucose, and lipids were normal in PCOS women. However, in vivo insulin sensitivity was slightly decreased (P = 0.03). Catecholamine-induced adipocyte lipolysis was markedly (i.e., about twofold) increased in PCOS women due to changes at the postreceptor level, although there was no change in the antilipolytic properties of visceral fat cells. Western blot analyses of visceral adipose tissue showed twofold increased levels of the catalytic and the regulatory la components of PKA. In contrast, the regulatory RIIbeta component of PKA was almost 50% decreased in visceral adipose tissue in PCOS women. Recent studies on genetically modified mice have shown that a similar transition in the regulatory PKA units induces an increased lipolytic response to catecholamines. Further analysis showed that the level of HSL-short, an enzymatically inactive splice form of HSL, was decreased in PCOS (P < 0.01). The altered lipolysis in PCOS is different from that observed in visceral fat cells in the insulin resistance syndrome that occurs at the level of adrenergic receptors. We concluded that increased catecholamine-induced lipolysis in visceral fat cells may be due to unique alterations in the stoichiometric properties of the adipose PKA-HSL holoenzymes. This could be an early and possibly primary lipolysis defect in PCOS.
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| 8. |
- Engert, JC, et al.
(författare)
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5 ' flanking variants of resistin are associated with obesity
- 2002
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 51:5, s. 1629-1634
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Tidskriftsartikel (refereegranskat)abstract
- Diabetes and obesity have long been known to be related. The recently characterized adipocyte hormone resistin (also called FIZZ3/ADSF) has been implicated as a molecular link between impaired glucose tolerance (IGT) and obesity in mice. A search for sequence variants at the human resistin locus identified nine single-nucleotide polymorphisms (SNPs) but no coding variants. An investigation into the association of these SNPs with diabetes and obesity revealed two 5' flanking variants (g.-537 and g.-420), in strong linkage disequilibrium, that are associated with BMI. In nondiabetic individuals from the Quebec City area and the Saguenay-Lac-St-Jean region of Quebec, the g.-537 mutation (allelic frequency = 0.04) was significantly associated with an increase in BMI (P = 0.03 and P = 0.01, respectively). When the data from these two populations were combined and adjusted for age and sex, both the g.-537 (odds ratio [OR] 2.72, 95% Cl 1.28-5.81) and the g.-420 variants (1.58, 1.06-2.35) were associated with an increased risk for a BMI greater than or equal to30 kg/m(2). In contrast, in case/control and family-based study populations from Scandinavia, we saw no effect on BMI with either of these promoter variants. No association was seen with diabetes in any of the population samples.
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| 9. |
- Engström, Gunnar, et al.
(författare)
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Inflammation-sensitive plasma proteins are associated with future weight gain.
- 2003
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 52:8, s. 2097-2101
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Tidskriftsartikel (refereegranskat)abstract
- Cross-sectional studies have associated obesity and other components of the so-called metabolic syndrome with low-grade inflammation. The temporal and causal relations of this association have not been fully explored. This study explored whether elevated levels of inflammation-sensitive plasma proteins (ISPs) (fibrinogen, orosomucoid, {alpha}1-antitrypsin, haptoglobin, and ceruloplasmin) are associated with future weight gain. Five ISPs were measured in 2,821 nondiabetic healthy men (38–50 years of age) who were reexamined after a mean follow-up of 6.1 years. Future weight gain was studied in relation to the number of elevated ISPs (i.e., in the top quartile). The proportion with a large weight gain (75th percentile >=3.8 kg) was 21.0, 25.9, 26.8, and 28.3%, respectively, among men with none, one, two, and three or more ISPs in the top quartile (P for trend 0.0005). This relation remained significant after adjustments for weight at baseline, follow-up time, height (at baseline and follow-up), physical inactivity (at baseline and follow-up), smoking (at baseline and follow-up), high alcohol consumption, and insulin resistance. The relations were largely similar for all individual ISPs. Elevated ISP levels predict a large weight gain in middle-aged men. This relation could contribute to the relation between inflammation, the metabolic syndrome, and cardiovascular disease. Several cross-sectional studies have reported positive correlations between body fatness and inflammation-sensitive plasma proteins (ISPs) and other inflammatory markers (1–4). Weight reduction in obese subjects has been associated with reduced inflammation (5–7). It has been proposed that proinflammatory cytokines formed in the adipose tissue, e.g., interleukin (IL)-6 and tumor necrosis factor-{alpha} (TNF-{alpha}), increase the hepatic synthesis of ISPs (4,8–10). However, the temporal and causal relations between obesity and elevated ISPs are incompletely understood. Even though inflammation is mainly considered an effect of obesity or weight increase, it also has been suggested that there could be a reverse relation, i.e., that inflammation could promote weight gain (11). A 3-year follow-up of the Atherosclerosis Risk in Communities (ARIC) study reported that a large weight gain was more common in subjects with elevated fibrinogen, white blood cells, von Willebrand factor, or factor VIII, i.e., four putative markers of inflammation (12). The Malmö Preventive Study cohort includes ~6,000 men with data on five ISPs (fibrinogen, haptoglobin, {alpha}1-antitrypsin, orosomucoid, and ceruloplasmin). Previous studies from this cohort have shown cross-sectional relations between ISP levels and BMI, blood pressure, and insulin resistance (1,13,14). Follow-up studies have shown that these proteins are associated with an increased incidence of cardiovascular diseases and an increased incidence of high blood pressure (15,16). The present study sought to explore whether these proteins predicted weight gain over a mean follow-up of 6 years.
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| 10. |
- Engström, Gunnar, et al.
(författare)
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Inflammation-sensitive plasma proteins, diabetes, and mortality and incidence of myocardial infarction and stroke: a population-based study.
- 2003
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 52:2, s. 442-447
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Tidskriftsartikel (refereegranskat)abstract
- This study explores the relationship of inflammation-sensitive plasma proteins (ISPs) with the prevalence of diabetes and the interrelationships between ISPs and diabetes in the prediction of death and incidence of myocardial infarction and stroke. Plasma levels of fibrinogen, α1-antitrypsin, haptoglobin, ceruloplasmin, and orosomucoid were assessed in 6,050 men, aged 28–61 years. All-cause and cardiovascular mortality and incidence of myocardial infarction and stroke were monitored over 18.7 ± 3.7 years. Prevalence of diabetes (n = 321) was significantly associated with ISP levels among overweight and obese men but not among men with BMI <25 kg/m2. The association was similar for insulin resistance according to homeostasis model assessment. High ISP levels (two or more ISPs in the top quartile) increased the cardiovascular risk among diabetic men. The risk factor-adjusted relative risks for cardiovascular mortality, myocardial infarction, and stroke were 2.8 (CI 1.8–4.5), 2.2 (1.5–3.2), and 2.5 (1.4–4.6), respectively, for diabetic men with high ISP levels (reference: nondiabetic men with low ISP levels). The corresponding risks for diabetic men with low ISP levels were 1.8 (1.1–3.0), 1.3 (0.8–2.1), and 1.2 (0.6–2.5), respectively. In conclusion, in this population-based cohort, diabetes was associated with increased ISP levels among overweight and obese men but not among men with normal weight. High ISP levels increased the cardiovascular risk similarly in diabetic as compared with nondiabetic men.
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