No abstract

As part of an ongoing search for diabetes susceptibility loci, we tested linkage with non-insulin-dependent diabetes mellitus (NIDDM) for 19 candidate loci or regions chosen for their potential to affect directly or indirectly the action of insulin. Loci were associated with insulin resistance, known effects on lipid metabolism, or effects on glucose metabolism or insulin action. Loci included the insulin-responsive (GLUT4) glucose transporter, hexokinase 2, glucagon, growth hormone, insulin receptor substrate 1 (IRS1), phosphoenolpyruvate carboxykinase, hepatic and muscle forms of pyruvate kinase, hepatic phosphofructokinase, the apolipoprotein B and the apolipoprotein A2 cluster, lipoprotein lipase, hepatic triglyceride lipase, the very-low-density-lipoprotein receptor, and the Pima insulin resistance locus on chromosome 4. For several candidates, no specific informative marker was available; consequently, we tested the surrounding region with highly informative markers. These regions included the diabetes-associated ras-like gene, rad, and the cholesterol ester-transfer gene, both mapped to chromosome 16. Additionally, we tested for linkage with markers at the tumor necrosis factor-alpha gene and the Friedreich's ataxia region. All regions were tested for linkage with microsatellite polymorphisms in > 450 individuals from a minimum of 16 Caucasian families under parametric (LINKAGE 5.1) and nonparametric (affected pedigree member) models.(ABSTRACT TRUNCATED AT 250 WORDS)

Considerable data support a genetic basis to susceptibility for NIDDM, but previous analysis of candidate genes has failed to identify a major susceptibility locus. Among regions with multiple potential candidates is chromosome 11, which includes the apolipoprotein C3 cluster, muscle glycogen phosphorylase, two insulin-dependent diabetes loci, the sulfonylurea receptor, and ataxia telangiectasia. To test linkage, we initially typed 19 markers at 10- to 15-cM intervals along chromosome 11. Analyses carried out under parametric models in members of 16-19 families of northern European ancestry detected possible linkage of NIDDM to D11S916. Nonparametric methods detected possible linkage to NIDDM at D11S901, which was 5- 10 cM distant, and at D11S935, which was approximately 30 cM distant. Both D11S916 and D11S901 were near the IDDM4 locus. To further test linkage, we typed five additional markers within 5 cM of D11S916 in the initial 19 families. We also tested markers from the linked region in a second set of recently sampled additional families. Two additional markers (D11S527 and D11S534) showed possible linkage in the initial 19 families, but none of the markers were linked to NIDDM in a separate set of families from the same ethnic background. The best evidence for linkage in the combined data set of the initial 19 families and 26 additional families was at D11S534 under parametric analysis (Z = 1.20) and at D11S935 under nonparametric analysis (affected pedigree number, P = 0.0013). Our findings suggest marginal evidence for a diabetes susceptibility locus in the region between D11S901 and D11S935, with the best evidence for a locus at or near D11S935. Replication of these findings in other populations will be necessary to distinguish false-positive linkage from a true NIDDM susceptibility locus.