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Background: Type 2 diabetes arises when insulin resistance-induced compensatory insulin secretion exhausts. Insulin resistance and/or beta-cell dysfunction result from the interaction of environmental factors (high-caloric diet and reduced physical activity) with a predisposing polygenic background. Very recently, genetic variations within four novel genetic loci (SLC30A8, HHEX, EXT2, and LOC387761) were reported to be more frequent in subjects with type 2 diabetes than in healthy controls. However, associations of these variations with insulin resistance and/or beta-cell dysfunction were not assessed., Methodology/principal Findings: By genotyping of 921 metabolically characterized German subjects for the reported candidate single nucleotide polymorphisms (SNPs), we show that the major alleles of the SLC30A8 SNP rs13266634 and the HHEX SNP rs7923837 associate with reduced insulin secretion stimulated by orally or intravenously administered glucose, but not with insulin resistance. In contrast, the other reported type 2 diabetes candidate SNPs within the EXT2 and LOC387761 loci did not associate with insulin resistance or beta-cell dysfunction, respectively., Conclusions/significance: The HHEX and SLC30A8 genes encode for proteins that were shown to be required for organogenesis of the ventral pancreas and for insulin maturation/storage, respectively. Therefore, the major alleles of type 2 diabetes candidate SNPs within these genetic loci represent crucial alleles for beta-cell dysfunction and, thus, might confer increased susceptibility of beta-cells towards adverse environmental factors.

Plasma homocysteine levels are elevated in individuals with type 2 diabetes contributing to the increased cardiovascular risk of these patients. As insulin resistance is a key feature in type 2 diabetic patients, hyperhomocysteinemia might be a consequence of insulin resistance. We studied this hypothesis in 839 individuals(male: 302, female: 537, mean age: 37.5 years) with a higher prevalence of insulin resistance (positive family history of type 2 diabetes, history of gestational diabetes, overweight). Subjects with overt type 2 diabetes or known kidney disease were excluded from the study. Mean plasma homocysteine concentration was 8.9 micromol/l (95% RCI 4.8-14.9). Adjusted for age and sex we could not find a significant correlation between homocysteine levels and BMI, insulin levels, or the insulin sensitivity-index (r = 0.35; p = 0.48). Furthermore, after a successful lifestyle intervention resulting in a significant decrease in BMI, body fat content and improved insulin sensitivity (p < 0.0001 each) no differences in homocysteine concentrations could be achieved. However,in the cross-sectional analysis we found a significant and independent, negative correlation between glomerular filtration rate (GFR) and homocysteine levels (r = -0.37; p < 0.0001). In conclusion, our study did not reveal a significant association between levels of homocysteine and insulin resistance in a population with an increased risk for type 2 diabetes. However, plasma homocysteine levels were related to subtle differences in kidney function at this early stage.

K-111 has been characterized as a potent peroxisome proliferator-activated receptor (PPAR)alpha activator. Antidiabetic potency and amelioration of disturbed lipid metabolism were demonstrated in rodents, which were accompanied by elevations of peroxisomal enzymes and liver weight. To examine the possible therapeutic application of K-111 we have now assessed its efficacy in non-human primates with high transferability to humans. For this purpose obese, hypertriglyceridaemic, hyperinsulinaemic prediabetic rhesus monkeys were dosed sequentially with 0, 1, 3 and 10mg/kg per day orally over a period of 4 weeks each. In addition, the effect of K-111 on the peroxisome compartment was analyzed in cynomolgus monkeys using liver samples obtained following a 13-week oral toxicity study. In prediabetic monkeys, the reduction of hyperinsulinaemia and improvement of insulin-stimulated glucose uptake rate indicated amelioration of insulin resistance. These effects were nearly maximal at a dose of 3mg/kg per day, while triglycerides and body weight were lowered significantly in a dose-dependent manner. This reduction of body weight contrasts sharply with the adipogenic response observed with thiazolidinediones, another family of insulin-sensitizing agents. In young cynomolgus monkeys at a dosage of 5mg/kg per day and more, K-111 induced an up to three-fold increase in lipid beta-oxidation enzymes with an 1.5- to 2-fold increase in peroxisome volume density. This moderate increase in peroxisomal activity by K-111 in monkeys is consistent with its role as an PPARalpha activator and corresponds to the observations with fibrates in other low responder mammalian species. The increase in beta-oxidation may explain, at least in part, the lipid modulating effect as well as the antidiabetic potency of K-111. This pharmacological profile makes K-111 a highly promising drug candidate for clinical applications in the treatment of type 2 diabetes, dyslipidaemia, obesity and the metabolic syndrome.