Type 1 diabetes is insulin -2221 MspI and CTLA-4 +49 A/G polymorphism dependent.
BACKGROUND
Several studies have demonstrated an association of type 1 diabetes with specific alleles of HLA class II molecules, as with polymorphisms of insulin gene region. The aim of our study was to evaluate the interaction of insulin -2221 MspI polymorphism to type 1 diabetes susceptibility in connection with autoimmunity associated gene--CTLA-4 polymorphism.


METHODS
Insulin -2221 MspI C/T and CTLA-4 +49 A/G polymorphisms were detected by restriction fragment-length polymorphism analysis or oligonucleotide hybridization in type 1 (n = 69), type 2 diabetes (n = 301) patients and 158 healthy controls. Regression model adjusted for age, gender and gene polymorphisms was studied.


RESULTS
C-allele of insulin -2221 MspI and G-allele of +49 CTLA-4 were significant risk factors for type 1 diabetes (crude OR 3.53 and 1.59, respectively) and this impact increased in the homozygous form of both alleles. The regression model supported the idea of insulin CC and CTLA-4 GG genotypes for an independent and clearly significant risk for developing type 1 diabetes. We could not detect any significant correlation between investigated polymorphisms and type 2 diabetes.


CONCLUSIONS
There exists a significant association between the C-allele of -2221 MspI in the insulin gene and type 1 diabetes. The CTLA-4 G-allele is also positively correlated with type 1 diabetes. According to the regression model the investigated gene polymorphisms are independent risk factors for development of type 1 diabetes in the Estonian population. We propose that -2221 MspI is a good marker for evaluation of risk of insulin gene haplotype in type 1 diabetes patients.
University of Tartu, Tartu, Estonia.
K
K
Haller
K
K
Kisand
V
V
Nemvalts
A-P
AP
Laine
J
J
Ilonen
R
R
Uibo
D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000235:genetics*; D060908:CTLA-4 Antigen; D016022:Case-Control Studies; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D007328:Insulin / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic / Q000235:genetics*; D012307:Risk Factors
D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D007328:Insulin