| 1. |
- Lyssenko, Valeriya, et al.
(författare)
-
Pleiotropic Effects of GIP on Islet Function Involve Osteopontin
- 2011
-
Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 60:9, s. 2424-2433
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE-The incretin hormone GIP (glucose-dependent insulinotropic polypeptide) promotes pancreatic beta-cell function by potentiating insulin secretion and beta-cell proliferation. Recently, a combined analysis of several genome-wide association studies (Meta-analysis of Glucose and Insulin-Related Traits Consortium [MAGIC]) showed association to postprandial insulin at the GIP receptor (GIPR) locus. Here we explored mechanisms that could explain the protective effects of GIP on islet function. RESEARCH DESIGN AND METHODS-Associations of GIPR rs10423928 with metabolic and anthropometric phenotypes in both nondiabetic (N = 53,730) and type 2 diabetic individuals (N = 2,731) were explored by combining data from 11 studies.Insulin secretion was measured both in vivo in nondiabetic subjects and in vitro in islets from cadaver donors. Insulin secretion was also measured in response to exogenous GIP. The in vitro measurements included protein and gene expression as well as measurements of beta-cell viability and proliferation. RESULTS-The A allele of GIPR rs10423928 was associated with impaired glucose- and GIP-stimulated insulin secretion and a decrease in BMI, lean body mass, and waist circumference. The decrease in BMI almost completely neutralized the effect of impaired insulin secretion on risk of type 2 diabetes. Expression of GIPR mRNA was decreased in human islets from carriers of the A allele or patients with type 2 diabetes. GIP stimulated osteopontin (OPN) mRNA and protein expression. OPN expression was lower in carriers of the A allele. Both GIP and OPN prevented cytokine-induced reduction in cell viability (apoptosis). In addition, OPN stimulated cell proliferation in insulin-secreting cells. CONCLUSIONS-These findings support beta-cell proliferative and antiapoptotic roles for GIP in addition to its action as an incretin hormone. Identification of a link between GIP and OPN may shed new light on the role of GIP in preservation of functional beta-cell mass in humans. Diabetes 60:2424-2433, 2011
|
|
| 2. |
- Jonsson, Anna, et al.
(författare)
-
A variant in the KCNQ1 gene predicts future type 2 diabetes and mediates impaired insulin secretion.
- 2009
-
Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 58:10, s. 2409-2413
-
Tidskriftsartikel (refereegranskat)abstract
- Objective- Two independent genome wide association studies for type 2 diabetes in Japanese have recently identified common variants in the KCNQ1 gene to be strongly associated with type 2 diabetes. Here we studied whether a common variant in KCNQ1 would influence BMI, insulin secretion and action and predict future type 2 diabetes in subjects from Sweden and Finland. Research design and methods- Risk of type 2 diabetes conferred by KCNQ1 rs2237895 was studied in 2,830 type 2 diabetes cases and 3,550 controls from Sweden (Malmö Case-Control) and prospectively in 16,061 individuals from the Malmö Preventive Project (MPP). Association between genotype and insulin secretion/action was assessed cross-sectionally in 3,298 non-diabetic subjects from the PPP-Botnia Study and longitudinally in 2,328 non-diabetic subjects from the Botnia Prospective Study (BPS). KCNQ1 expression (n=18) and glucose-stimulated insulin secretion (n=19) was measured in human islets from non-diabetic cadaver donors. Results. The C-allele of KCNQ1 rs2237895 was associated with increased risk of type 2 diabetes in both the case-control (OR 1.23 [1.12-1.34], p=5.6x10(-6)) and the prospective (OR 1.14 [1.06-1.22], p=4.8x10(-4)) studies. Furthermore, the C-allele was associated with decreased insulin secretion (CIR p=0.013; DI p=0.013) in the PPP-Botnia study and in the BPS at baseline (CIR p=3.6x10(-4); DI p=0.0058) and after follow-up (CIR p=0.0018; DI p=0.0030). C-allele carriers showed reduced glucose-stimulated insulin secretion in human islets (p=2.5x10(-6)). Conclusion. A common variant in the KCNQ1 gene is associated with increased risk of future type 2 diabetes in Scandinavians which partially can be explained by an effect on insulin secretion.
|
|
