| 1. |
- Kalis, Martins
(författare)
-
Beta Cell Function: from Human Genetics to Animal Models
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Beta cell function is an important factor in the development of both Type 1 (T1D) and Type 2 (T2D) diabetes mellitus. T1D is characterized by a primary defect in insulin secretion due to the immune-mediated beta cell destruction, however, the more common T2D beside insulin resistance also include impaired beta cell function as a consequence to abnormal glucose homeostasis. Genetic susceptibility is involved in both types of diabetes. We have studied several genetic and immunological factors affecting beta cell function. First, we tested whether single nucleotide polymorphisms (SNPs) of the human Free Fatty Acid Receptor 1 (FFAR1) are associated with T2D and insulin secretion. Another genetic study focused on FOXP3 association with T1D and the disease-related clinical parameters. The role of microRNAs (miRNAs) on beta cell function was studied in the third project using a novel genetically engineered mouse model. Subsequently, the effect of Alpha 1-Antitrypsin (AAT) on cytokine-induced apoptosis and on insulin secretion was studied in beta cells in vitro. In Study I, we concluded that SNPs rs1978013 and rs1978014 in the upstream region of FFAR1 gene might contribute to impaired beta cell function in T2D. Study II showed that the minor A allele in the FOXP3 rs2232365 SNP might represent a protective factor in T1D pathogenesis and suggest a possible role of FOXP3 in the regulation of autoimmunity against pancreatic beta cells. We have demonstrated for the first time in Study III that targeted disruption of the Dicer1 gene specifically in beta cells leads to progressive impairment of insulin secretion and diabetes development. Our findings of Study IV show that AAT stimulates insulin secretion and protects beta cells against cytokine-induced apoptosis, and these effects of AAT seems to be mediated through the cAMP pathway.
|
|
| 2. |
- Kalis, Martins, et al.
(författare)
-
Beta-cell specific deletion of dicer1 leads to defective insulin secretion and diabetes mellitus
- 2011
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:12, s. e29166-
-
Tidskriftsartikel (refereegranskat)abstract
- Mature microRNAs (miRNAs), derived through cleavage of pre-miRNAs by the Dicer1 enzyme, regulate protein expression in many cell-types including cells in the pancreatic islets of Langerhans. To investigate the importance of miRNAs in mouse insulin secreting beta-cells, we have generated mice with a beta-cells specific disruption of the Dicer1 gene using the Cre-lox system controlled by the rat insulin promoter (RIP). In contrast to their normoglycaemic control littermates (RIP-Cre(+/-) Dicer1(Delta/wt)), RIP-Cre(+/-) Dicer1(flox/flox) mice (RIP-Cre Dicer1(Delta/Delta)) developed progressive hyperglycaemia and full-blown diabetes mellitus in adulthood that recapitulated the natural history of the spontaneous disease in mice. Reduced insulin gene expression and concomitant reduced insulin secretion preceded the hyperglycaemic state and diabetes development. Immunohistochemical, flow cytometric and ultrastructural analyses revealed altered islet morphology, marked decreased beta-cell mass, reduced numbers of granules within the beta-cells and reduced granule docking in adult RIP-Cre Dicer1(Delta/Delta) mice. beta-cell specific Dicer1 deletion did not appear to disrupt fetal and neonatal beta-cell development as 2-week old RIP-Cre Dicer1(Delta/Delta) mice showed ultrastructurally normal beta-cells and intact insulin secretion. In conclusion, we have demonstrated that a beta-cell specific disruption of the miRNAs network, although allowing for apparently normal beta-cell development, leads to progressive impairment of insulin secretion, glucose homeostasis and diabetes development.
|
|
| 3. |
- Kalis, Martins, et al.
(författare)
-
Variants in the FFAR1 Gene Are Associated with Beta Cell Function
- 2007
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 2:11
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The FFAR1 receptor is expressed mainly in pancreatic beta cells and is activated by medium to long chain free fatty acids (FFAs), as well as by thiazolidinediones, resulting in elevated Ca(2+) concentrations and promotion of insulin secretion. These properties suggest that FFAR1 could be a mediator of lipotoxicity and a potential candidate gene for Type 2 diabetes (T2D). We therefore investigated whether variations at the FFAR1 locus are associated with T2D and beta cell function. METHODOLOGY/PRINCIPAL FINDINGS: We re-sequenced the FFAR1 region in 96 subjects (48 healthy and 48 T2D individuals) and found 13 single nucleotide polymorphisms (SNPs) 8 of which were not previously described. Two SNPs located in the upstream region of the FFAR1 gene (rs1978013 and rs1978014) were chosen and genotyped in 1929 patients with T2D and 1405 healthy control subjects. We observed an association of rs1978013 and rs1978014 with insulinogenic index in males (p = 0.024) and females (p = 0.032), respectively. After Bonferroni corrections, no association with T2D was found in the case-control material, however a haplotype consisting of the T-G alleles conferred protection against T2D (p = 0.0010). CONCLUSIONS/SIGNIFICANCE: Variation in the FFAR1 gene may contribute to impaired beta cell function in T2D.
|
|
| 4. |
- Kalis, Martins, et al.
(författare)
-
α 1-antitrypsin enhances insulin secretion and prevents cytokine-mediated apoptosis in pancreatic β-cells.
- 2010
-
Ingår i: Islets. - : Informa UK Limited. - 1938-2022 .- 1938-2014. ; 2:3, s. 185-189
-
Tidskriftsartikel (refereegranskat)abstract
- α1-antitrypsin (AAT) is a serine protease inhibitor, which recently has been shown to prevent type 1 diabetes (T1D) development, to prolong islet allograft survival and to inhibit β-cell apoptosis in vivo. It has also been reported that T1D patients have significantly lower plasma concentrations of AAT suggesting the potential role of AAT in the pathogenesis of T1D. We have investigated whether plasma-purified AAT can affect β-cell function in vitro. INS-1E cells or primary rat pancreatic islets were used to study the effect of AAT on insulin secretion after glucose, glucagon-like peptide-1 (GLP-1) and forskolin stimulation and on cytokine-mediated apoptosis. The secreted insulin and total cyclic AMP (cAMP) were determined using radioimmunoassay and apoptosis was evaluated by propidium iodide staining followed by FACS analysis. We found that AAT increases insulin secretion in a glucose-dependent manner, potentiates the effect of GLP-1 and forskolin and neutralizes the inhibitory effect of clonidine on insulin secretion. The effect of AAT on insulin secretion was accompanied by an increase in cAMP levels. In addition, AAT protected INS-1E cells from cytokine-induced apoptosis. Our findings show that AAT stimulates insulin secretion and protects β-cells against cytokine-induced apoptosis, and these effects of AAT seem to be mediated through the cAMP pathway. In view of these novel findings we suggest that AAT may represent a novel anti-inflammatory compound to protect β-cells under the immunological attack in T1D but also therapeutic strategy to potentiate insulin secretion in type 2 diabetes (T2D).
|
|
