Association of the ENPP1 K121Q polymorphism with type 2 diabetes and obesity in the Moroccan population

Abstract

The ectonucleotide pyrophosphatase/phosphodiesterase 1 enzyme (ENPP1), which downregulates insulin signaling by inhibiting insulin-receptor tyrosine kinase activity, is encoded by the ENPP1 gene. A common functional ENPP1 K121Q polymorphism has been suggested to contribute to insulin resistance, obesity and type 2 diabetes (T2D) in various ethnic groups. For this reason, we assessed the association between the ENPP1 K121Q polymorphism in T2D and obesity phenotypes in the Moroccan population. Using LightCycler((R)) technology, we genotyped the ENPP1 K121Q polymorphism in 503 subjects with T2D and 412 normoglycaemic individuals. There was no evidence of an association between ENPP1 K121Q and T2D in either an additive (P=0.99) or recessive mode of inheritance (P=0.47). However, the Q121 variant was significantly more frequent in obese than in non-obese subjects after adjusting for age, gender and T2D status. We observed genetic heterogeneity between obese and non-obese T2D patients (P=0.02). The K121Q polymorphism was associated with T2D in the presence of obesity in both additive (1.55 [95% CI 1.16-2.07]; P=0.003) and recessive (2.31 [95% CI 1.34-3.97]; P=0.002) modes of inheritance. Although there was no evidence of an association between the ENPP1 K121Q variant and the general phenotype of T2D, we did find an association with adult obesity and T2D. The Q121 allele frequency in Morocco is 37.3%, placing it between European Caucasians (15%) and Black Africans (79%). This study is the first to report an association between K121Q and metabolic diseases in the Moroccan population.