Association of indices of liver and adipocyte insulin resistance with 19 confirmed susceptibility loci for type 2 diabetes in 6,733 non-diabetic Finnish men

Of the confirmed type 2 diabetes susceptibility loci only a few are known to affect insulin sensitivity. We examined the association of indices of hepatic and adipocyte insulin resistance (IR) with 19 confirmed type 2 diabetes risk loci in a large population-based study. Non-diabetic participants (n = 8,460, age 57.3 +/- 7.0 years, BMI 26.8 +/- 3.8 kg/m(2); mean +/- SD) from a population-based cohort underwent an OGTT. Of them, 6,733 non-diabetic men were genotyped for single nucleotide polymorphisms (SNPs) in or near PPARG2 (also known as PPARG), KCNJ11, TCF7L2, SLC30A8, HHEX, CDKN2B, IGF2BP2, CDKAL1, HNF1B, WFS1, JAZF1, CDC123, TSPAN8, THADA, ADAMTS9, NOTCH2, KCNQ1, MTNR1B and SNP rs7480010. We investigated hepatic IR with a new index of liver IR. The adipocyte IR index was defined as a product of fasting NEFA and plasma insulin levels. Type 2 diabetes risk SNPs in or near KCNJ11 and HHEX were significantly (p < 0.0013), and those in or near CDKN2B, NOTCH2 and MTNR1B were nominally (p < 0.05), associated with decreased liver IR index. The Pro12 allele of PPARG2 was significantly associated with a high adipocyte IR index and nominally associated with high liver IR. The Pro12 allele of PPARG2 seems to impair insulin's antilipolytic effect, leading to high NEFA release in the fasting state and IR. In addition, the type 2 diabetes risk alleles of KCNJ11 and HHEX, which are known to impair insulin secretion, were associated with increased hepatic insulin sensitivity.