Polymorphisms within Novel Risk Loci for Type 2 Diabetes Determine β-Cell Function

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

Association of obesity risk SNPs in PCSK1 with insulin sensitivity and proinsulin conversion

<p>Abstract</p> <p>Background</p> <p>Prohormone convertase 1 is involved in maturation of peptides. Rare mutations in gene <it>PCSK1</it>, encoding this enzyme, cause childhood obesity and abnormal glucose homeostasis with elevated proinsulin concentrations. Common single nucleotide polymorphisms (SNPs) within this gene, rs6232 and rs6235, are associated with obesity. We studied whether these SNPs influence the prediabetic traits insulin resistance, β-cell dysfunction, or glucose intolerance.</p> <p>Methods</p> <p>We genotyped 1498 German subjects for SNPs rs6232 and rs6235 within <it>PCSK1</it>. The subjects were metabolically characterized by oral glucose tolerance test with glucose, insulin, proinsulin, and C-peptide measurements. A subgroup of 512 subjects underwent a hyperinsulinemic-euglycemic clamp.</p> <p>Results</p> <p>The minor allele frequencies were 25.8% for SNP rs6235 and 6.0% for rs6232. After adjustment for sex and age, we found no association of SNPs rs6235 and rs6232 with BMI or other weight-related traits (all p ≥ 0.07). Both minor alleles, adjusted for sex, age, BMI and insulin sensitivity were associated with elevated AUC_proinsulinand AUC_proinsulin/AUC_insulin(rs6235: p_{additive model}≤ 0.009, effect sizes 8/8%, rs6232: p_{dominant model}≤ 0.01, effect sizes 10/21%). Insulin secretion was not affected by the variants (different secretion parameters, all p ≥ 0.08). The minor allele of SNP rs6232 was additionally associated with 15% higher OGTT-derived and 19% higher clamp-derived insulin sensitivity (p_dom≤ 0.0047), 4.5% lower HOMA_IR(p_dom= 0.02) and 3.5% lower 120-min glucose (p_dom= 0.0003) independently of BMI and proinsulin conversion. SNP rs6235 was not associated with parameters of glucose metabolism.</p> <p>Conclusions</p> <p>Like rare mutations in <it>PCSK1</it>, the more common variants tested determine glucose-stimulated proinsulin conversion, but not insulin secretion. In addition, rs6232, encoding the amino acid exchange N221D, influences insulin sensitivity and glucose homeostasis.</p

Evaluation of the efficacy, safety and tolerability of orally administered BI 409306, a novel phosphodiesterase type 9 inhibitor, in two randomised controlled phase II studies in patients with prodromal and mild Alzheimer’s disease

International audienceBACKGROUND: There are currently no approved treatments for the prodromal stage of Alzheimer's disease (AD). Approved symptomatic treatments for mild-to-moderate AD include acetylcholinesterase inhibitors and memantine, but more efficacious treatments are needed. BI 409306 is a potent and selective phosphodiesterase 9 inhibitor assessed for the symptomatic treatment of AD. Efficacy and safety of BI 409306 was analysed in two phase II proof-of-concept clinical trials in cognitive impairment associated with prodromal AD (study 1) and mild AD (study 2).METHODS: Two multicentre, double-blind, parallel-group, randomised controlled phase II studies were conducted (North America/Europe). Following study run-in, eligible subjects were randomised to one of four oral doses of BI 409306 (10-50 mg daily) or placebo (1:1:1:1:2 ratio) for 12 weeks. The primary efficacy endpoint was the change from baseline in Neuropsychological Test Battery (NTB) total z-score after 12 weeks' treatment. Secondary efficacy assessments included change from baseline in Clinical Dementia Rating scale-Sum of Boxes (CDR-SB), Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-Cog11) and Alzheimer's Disease Cooperative Study-Activities of Daily Living scale (ADCS-ADL; mild cognitive impairment [MCI] version for prodromal patients) after 12 weeks' treatment. Safety and tolerability assessments included adverse event reporting and vital sign monitoring. Change from baseline in NTB total z-score (primary endpoint) and CDR-SB were analysed using the restricted maximum likelihood-based mixed-effects model with repeated measurement. An analysis of covariance model was used to assess other secondary endpoints.RESULTS: Four hundred fifty-seven patients were randomised (study 1 for prodromal AD, N = 128; study 2 for mild AD, N = 329); 427 (93.4%) completed. A prespecified pooled analysis of the primary endpoint revealed no significant changes in NTB total composite z-score at week 12 in the BI 409306 treatment groups compared with placebo, with similar findings observed in the individual studies. The analysis of all secondary endpoints, including pooled analysis of CDR-SB and ADAS-Cog11, ADCS-MCI-ADL (study 1), ADCS-ADL (study 2), also gave no indication of a treatment benefit for BI 409306, compared with placebo. BI 409306 was well tolerated.CONCLUSIONS: Overall, the data do not demonstrate efficacy of BI 409306 in improving cognition in patients with prodromal and mild AD. BI 409306 is well tolerated