Association between interleukin-1 gene polymorphism and severity of chronic periodontitis in a south Indian population group

BACKGROUND: Periodontitis is a bacterial disease modified by multiple factors. Interleukin-1 (IL-1) is a key regulator of the host response and a major modulator of extracellular matrix catabolism and bone resorption. It has been reported that variations in IL-1 gene are associated with increased susceptibility to periodontitis. The aims of the study were 1) to analyze the distribution of single nucleotide polymorphism of IL-1 (IL-1A-+4845 and IL-1B-+3954) and 2) to correlate the association of the composite genotype with the severity of chronic periodontitis. MATERIALS AND METHODS: Sixty patients aged above 35 years were selected. Following a periodontal examination, using the clinical parameters plaque index, gingival bleeding index, probing depth, and clinical attachment loss (CAL), the selected subjects were categorized into four groups of differing disease severity based on CAL. Five milliliters of venous blood was drawn. DNA was isolated by phenol chloroform method. Amplification of IL-1A+4845 and IL-1B+3954 was done by polymerase chain reaction (PCR). Detection of genotype was done using restriction fragment length polymorphism using the enzymes FnU4HI for IL-1A and TaqI for IL-1B. The results obtained were analyzed statistically. RESULTS: The frequencies of IL-1A-+4845 and IL-1B-+3954were significantly greater in severe periodontitis patients. The distribution of composite genotype (allele 2 of IL-1A+4845and allele 2 of IL-1B+3954) also correlated with the severity of periodontitis. Genotype-positive subjects had a higher mean bleeding index (%) when compared to genotype-negative patients. But no correlation was observed between mean plaque level among genotype-positive and -negative subjects. CONCLUSION: IL-1 gene polymorphism IL-1A+4845, IL-1B+3954 and composite genotype is an indicator of susceptibility to severe periodontitis in adults.