| 1. |
- Blixt, Martin, 1977-, et al.
(författare)
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Characterization of β-cell function of pancreatic islets isolated from bank voles developing glucose intolerance/diabetes : an animal model showing features of both type 1 and type 2 diabetes mellitus, and a possible role of the Ljungan virus
- 2007
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 154:1-3, s. 41-47
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Tidskriftsartikel (refereegranskat)abstract
- Bank voles (Clethrionomys glareolus) kept in captivity develop diabetes mellitus to a significant extent. Also in wild bank voles, elevated blood glucose has been observed. A newly isolated picornavirus named Ljungan virus (LV) has been found in the pancreas of these bank voles. Moreover, LV infection in combination with environmental factors may cause glucose intolerance/diabetes (GINT/D) in normal mice. The aim of the present study was to investigate the functional characteristics of pancreatic islets, isolated from bank voles, bred in the laboratory but considered LV infected. About 20% of all males and females were classified as GINT/D following a glucose tolerance test. Of these animals the majority had become diabetic by 20 weeks of age, with a tendency towards an earlier onset in the males. GINT/D animals had increased serum insulin levels. Islets were tested on the day of isolation (day 0) and after 1 week of culture for their insulin content and their capacity to synthesize (pro)insulin, secrete insulin and metabolize glucose. Functional differences could be observed between normal and GINT/D animals as well as between genders. An elevated basal insulin secretion was observed on day 0 indicating β-cell dysfunction among islets isolated from diabetic males. In vitro culture could reverse some functional changes. The increased serum insulin level and the increased basal islet insulin secretion may suggest that the animals had developed a type 2 diabetes-like condition. It is likely that the putative stress imposed in the laboratory, maybe in combination with LV infection, can lead to an increased functional demand on the β-cells.
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| 2. |
- Blixt, Martin, 1977-, et al.
(författare)
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Suppression of bank vole pancreatic islet function by proinflammatory cytokines
- 2009
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Ingår i: Molecular and Cellular Endocrinology. - : Elsevier BV. - 0303-7207 .- 1872-8057. ; 305:1-2, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- Bank voles kept in captivity may develop diabetes. We recently characterized beta-cell function of pancreatic islets from normal and glucose intolerant/diabetic bank voles. These animals had features of both human type 1 and type 2 diabetes. Cytokines may impair β-cell function in both types of diabetes. Presently, we studied how pancreatic islets isolated from normal, i.e. glucose tolerant bank voles are affected by proinflammatory cytokines in vitro. Islets were exposed to hIL-1β (25U/ml) alone or in combination with hTNF-α (1000U/ml)+mIFN-γ (1000U/ml) for 48h, whereupon islet functions were assessed. Cytokines markedly reduced insulin gene expression and the (pro)insulin biosynthesis rate, which was accompanied by a profound depletion of the islet insulin content. The cytokines did not affect the culture medium insulin accumulation and the glucose oxidation rate, but caused a modest increase in medium nitrite, an indicator of nitric oxide (NO) generation. Cytokine-induced decrease in islet insulin content was not prevented by the preferential inducible NO synthase inhibitor aminoguanidine. These findings suggest that the reduction in islet insulin content is not attributed to enhanced exocytosis or related to altered glucose metabolism, but is rather due to a decline in insulin production. The suppressive effects of islet functions elicited by cytokines seem to be mediated by an NO-independent mechanism. In relation to previous studies on cytokine effects on islets from various species, the bank vole islets show a pattern which more resembles human islets than rat or murine islets.
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| 3. |
- Ekström, Jens-Ola, et al.
(författare)
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Replication of Ljungan virus in cell culture : the genomic 5'-end, infectious cDNA clones and host cell response to viral infections
- 2007
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Ingår i: Virus Research. - : Elsevier BV. - 0168-1702 .- 1872-7492. ; 130:1-2, s. 129-139
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Tidskriftsartikel (refereegranskat)abstract
- Ljungan virus (LV) is a picornavirus recently isolated from bank voles (Clethrionomys glareolus). The previously uncharacterised 5'-end sequence of the LV genome was determined. Infectious cDNA clones were constructed of the wild type LV prototype strain 87-012 and of the cytolytically replicating cell culture adapted variant 87-012G. Virus generated from cDNA clones showed identical growth characteristics as uncloned virus stocks. Cell culture adapted LV, 87-012G, showed a clear cytopathic effect (CPE) at 3-4 days post-infection (p.i.). Virus titers, determined by plaque titration, increased however only within the first 18h p.i. Replication of LV (+) strand RNA was determined by real-time PCR and corresponded in time with increasing titers. In contrast, the amounts of the replication intermediate, the (-) strand, continued to increase until the cells showed CPE. This indicates separate controlling mechanisms for replication of LV (+) and (-) genome strands. Replication was also monitored by immunofluorescence (IF) staining. IF staining of both prototype 87-012 and the CPE causing 87-012G showed groups of 5-25 infected cells at 48h p.i., suggesting a, for picornaviruses, not previously described direct cell-to-cell transmission.
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| 4. |
- Holmberg, Rebecka, et al.
(författare)
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Antiviral treatments reduce severity of diabetes in Ljungan virus-infected CD-1 mice and delay onset in diabetes-prone BB rats
- 2009
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Ingår i: Microbiology and immunology. - : Wiley. - 0385-5600 .- 1348-0421. ; 53:10, s. 567-572
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Tidskriftsartikel (refereegranskat)abstract
- The effects of LV in two different species, CD-1 mice, without a genetic disposition for diabetes, and BB rats prone to T1D were examined. Male CD-1 mice that had been exposed to LV in utero developed a type 2-like diabetes with increased blood glucose, insulin levels and epididymal fat at the age of 10-15 weeks. Combination therapy including LV-antiserum and an antiviral drug, Pleconaril, significantly reduced the levels of blood glucose and insulin and the amount of abdominal fat. In BB rats, LV has been found in both prediabetic- and diabetic diabetes-prone rats, as well as in diabetes-resistant rats. To evaluate whether the presence of LV has any influence on the onset of T1D, prediabetic BB rats were treated with an antiserum against LV or a combination of the antiviral drugs Pleconaril and Ribavirin. In the group treated with antiviral drugs, the onset was significantly delayed. These results indicate that the presence of LV can be involved in the pathogenesis of diabetes in these animal models.
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| 5. |
- Mantke, Oliver Donoso, et al.
(författare)
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A new quantitative real-time reverse transcriptase PCR assay and melting curve analysis for detection and genotyping of Ljungan virus strains
- 2007
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Ingår i: Journal of Virological Methods. - : Elsevier BV. - 0166-0934 .- 1879-0984. ; 141:1, s. 71-77
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Tidskriftsartikel (refereegranskat)abstract
- Ljungan virus (LV), a new member of the Picornaviridoe, recently isolated from vole species in both Sweden and the USA, is suspected to be pathogenic for humans as an actiological agent in myocarditis, diabetes, neurological disease and perinatal disease. This study describes for the first time an RT-PCR assay that can identify and quantify LV infection in various tissue sample types using primers and two different minor-groove-binder probes targeting the 5'-untranslated region of the LV genome. The assay, evaluated using control samples derived from various virus cultures and rodent tissues, allows precise quantification of viral load over six orders of magnitude (101 to 106 viral copies per assay) for all known strains of LV with high sensitivity and specificity. Furthermore, a melting curve analysis (MCA) was developed using two amplicon-specific hybridisation probes that allows rapid genotyping of different LV strains. These new methods provide useful tools to investigate the putative role of LV as a pathogen in both rodents and humans.
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| 6. |
- Niklasson, Bo, et al.
(författare)
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Association of zoonotic Ljungan virus with intrauterine fetal deaths
- 2007
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Ingår i: Birth defects research. Clinical and molecular teratology. - : Wiley. - 1542-0752 .- 1542-0760. ; 79, s. 488-493
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: It has recently been shown that Ljungan virus (LV) is associated with disease in its wild rodent reservoir. In addition, it has been demonstrated that LV causes malformations and perinatal death in a mouse model. The question was therefore raised whether LV is a zoonotic agent in humans. METHODS: Population fluctuations of native rodents in Sweden were compared to the incidence of intrauterine fetal deaths (IUFDs) using the Swedish national hospitalization database. Formalin-fixed tissues from cases of IUFD were investigated using LV-specific immunohistochemistry. RESULTS: Variation in the incidence of IU-FDs closely tracked the fluctuations in native rodent populations. LV was detected in the brain tissue in 4 of 10 cases of IUFDs investigated by immunochemistry. LV was also detected in the placenta in 5 of the 10 IUFD cases, but in none of 20 placentas from normal pregnancies. CONCLUSIONS: LV may play an important role in IUFDs.
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| 7. |
- Niklasson, Bo, et al.
(författare)
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Diabetes and myocarditis in voles and lemmings at cyclic peak densities--induced by Ljungan virus?
- 2006
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 150:1, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Although it is well-documented from theoretical studies that pathogens have the capacity to generate cycles, the occurrence and role of pathogens and disease have been poorly empirically studied in cyclic voles and lemmings. In screening for the occurrence of disease in cyclic vole and lemming populations, we found that a high proportion of live-trapped Clethrionomys glareolus, C. rufocanus, Microtus agrestis and Lemmus lemmus at high collective peak density, shortly before the decline, suffered from diabetes or myocarditis in northern Scandinavia. A high frequency of animals had abnormal blood glucose (BG) levels at the time of trapping (5-33%). In contrast, C. rufocanus individuals tested at a much lower overall density, and at an earlier stage relative to the decline in the following cycle, showed normal BG concentrations. However, a high proportion (43%) of a sample of these individuals kept in captivity developed clinical diabetes within five weeks, as determined by BG levels and a glucose tolerance test performed at that later time. A new picornavirus isolated from the rodents, Ljungan virus (LV), was assumed to cause the diseases, as LV-induced diabetes and myocarditis, as well as encephalitis and fetal deaths, were observed in laboratory mice. We hypothesize that LV infection significantly affects morbidity and mortality rates in the wild, either directly or indirectly, by predisposing the rodents to predation, and is at least involved in causing the regular, rapid population declines of these cyclic voles and lemmings. Increased stress at peak densities is thought to be an important trigger for the development of disease, as the occurrence of disease in laboratory mice has been found to be triggered by introducing stress to LV-infected animals.
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| 8. |
- Niklasson, Bo, et al.
(författare)
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Prenatal viral exposure followed by adult stress produces glucose intolerance in a mouse model
- 2006
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 0012-186X .- 1432-0428. ; 49:9, s. 2192-2199
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Tidskriftsartikel (refereegranskat)abstract
- Aims/hypothesis: It has been suggested that the uterine environment may influence metabolic disease occurring later in adult life, and that adult stress may promote disease outcome. Using a mouse model, we tested whether in utero exposure to Ljungan virus (LV) followed by adult exposure to stress produces diabetes. The influence of the timing of viral exposure over the course of pregnancy was also tested. Materials and methods: Pregnant CD-1 mice were exposed i.p. to LV on pregnancy days 4, 8, 12 or 17. Adult male mice from these pregnancies were stressed by being kept in shared cages. Stress only, LV exposure in utero only, and no-stress/no virus exposure groups were also followed. Outcome variables included bodyweight, epididymal fat weight, baseline glucose, glucose tolerance tests (60 and 120 min) and serum insulin. Results: We demonstrated that male mice developed a type 2-like diabetes, including obesity, as adults if infected during pregnancy with LV. Diabetes at the age of 11 weeks was more severe in mice whose mothers were infected earlier than in those whose mothers were infected later in pregnancy. Only animals infected in utero and kept under stress developed diabetes; infection or stress alone did not cause disease. Conclusions/interpretation: This work demonstrates that a type 2 diabetes-like disease can be virus-induced in a mouse model. Early in utero viral insults can set the stage for disease occurring during adult life, but the final manifestation of diabetes is dependent on the combination of early viral exposure and stress in adult life.
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| 9. |
- Niklasson, Bo, et al.
(författare)
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Sudden infant death syndrome and Ljungan virus
- 2009
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Ingår i: Forensic Science, Medicine, and Pathology. - Totowa : Springer Science and Business Media LLC. - 1547-769X .- 1556-2891. ; 5:4, s. 274-279
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Tidskriftsartikel (refereegranskat)abstract
- Ljungan virus (LV) has recently been associated with perinatal death in its natural rodent reservoir and also with developmental disorders of reproduction in laboratory mice. A strong epidemiological association has been found between small rodent abundance in Sweden and the incidence of intrauterine fetal death (IUFD) in humans. LV antigen has been detected in half of the IUFD cases tested. The question was therefore raised whether sudden infant death syndrome (SIDS) might be associated with rodent abundance, and whether the virus is present in cases of SIDS. Variation in the incidence of SIDS using the Swedish cause-of-death database tracked the changes in the population fluctuations of native rodents. Formalin-fixed tissues from the brain, heart, and lung were investigated from cases of SIDS, SIDS with lymphocytic infiltration of the myocardium (myocarditis) and myocarditis cases using LV specific immunohistochemistry (IHC). Ljungan virus was detected in the brain, heart, and lung tissue from all three of the patient categories investigated using IHC. These studies suggest that LV may play a prominent role in infant death, and that IUFD and SIDS may have common etiological underpinnings.
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| 10. |
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