New Locus for Skin Intrinsic Fluorescence in Type 1 Diabetes Also Associated With Blood and Skin Glycated Proteins

Genome-wide association study identifies novel loci associated with skin autofluorescence in individuals without diabetes

BACKGROUND

Skin autofluorescence (SAF) is a non-invasive measure reflecting accumulation of advanced glycation endproducts (AGEs) in the skin. Higher SAF levels are associated with an increased risk of developing type 2 diabetes and cardiovascular disease. An earlier genome-wide association study (GWAS) revealed a strong association between NAT2 variants and SAF. The aim of this study was to calculate SAF heritability and to identify additional genetic variants associated with SAF through genome-wide association studies (GWAS).

RESULTS

In 27,534 participants without diabetes the heritability estimate of lnSAF was 33% ± 2.0% (SE) in a model adjusted for covariates. In meta-GWAS for lnSAF five SNPs, on chromosomes 8, 11, 15 and 16 were associated with lnSAF (P < 5 × 10^-8): 1. rs2846707 (Chr11:102,576,358,C > T), which results in a Met30Val missense variant in MMP27 exon 1 (NM_022122.3); 2. rs2470893 (Chr15:75,019,449,C > T), in intergenic region between CYP1A1 and CYP1A2; with attenuation of the SNP-effect when coffee consumption was included as a covariate; 3. rs12931267 (Chr16:89,818,732,C > G) in intron 30 of FANCA and near MC1R; and following conditional analysis 4. rs3764257 (Chr16:89,800,887,C > G) an intronic variant in ZNF276, 17.8 kb upstream from rs12931267; finally, 30 kb downstream from NAT2 5. rs576201050 (Chr8:18,288,053,G > A).

CONCLUSIONS

This large meta-GWAS revealed five SNPs at four loci associated with SAF in the non-diabetes population. Further unravelling of the genetic architecture of SAF will help in improving its utility as a tool for screening and early detection of diseases and disease complications.

NAT2 gene polymorphisms and endometriosis risk: A PRISMA-compliant meta-analysis

OBJECTIVE

Endometriosis is a common chronic, gynecological disease. Despite many studies on the role of N-acetyltransferase 2 (NAT2) in endometriosis, its clinical significance is unclear. In this study, associations between NAT2 phenotypes as well as single nucleotide polymorphisms (SNPs) within NAT2 (i.e. rs1799929, rs1799930, rs1208, and rs1799931) and endometriosis risk were evaluated using a meta-analysis approach.

METHODS

Embase, PubMed, ClinicalTrials.gov, CNKI (China National Knowledge Infrastructure), Wanfang databases, Cochrane Library for clinical trials, and Web of Science were searched to identify relevant articles. ORs (odds ratios) and 95% CIs (95% confidence intervals) were used to estimate the associations between NAT2 polymorphisms and endometriosis risk. Heterogeneity among included studies was also assessed. In addition, a subgroup analysis of NAT2 phenotypes and endometriosis risk based on ethnicity was performed.

RESULTS

Nine case-control studies met the inclusion criteria. The odds ratio was 2.30 (95% CI: 1.61-3.28) for the NAT2 slow acetylation phenotype versus the intermediate + fast acetylation phenotype in the Asian population. These results suggest that Asian individuals with the NAT2 slow acetylation phenotype have a 130% increased risk of endometriosis. A significant association was also found for rs1799930 (OR = 0.74; 95% CI, 0.59-0.92), suggesting that individuals with this mutant genotype have a 26% decreased risk of endometriosis.

CONCLUSIONS

The rs1799930 mutant genotypes are associated with a decreased risk of endometriosis. No statistically significant associations were found between rs1799931, rs1208, or rs1799929 and endometriosis. Based on a subgroup analysis based on ethnicity, the NAT2 slow acetylation phenotype was found to increase the risk of endometriosis in Asians. No statistically significant associations were found between the NAT2 slow acetylation phenotype and endometriosis risk in Caucasians. Accordingly, NAT2 phenotypes and SNPs are potential biomarkers for the diagnosis and treatment of endometriosis.

Screening Human Embryos for Polygenic Traits Has Limited Utility

The increasing proportion of variance in human complex traits explained by polygenic scores, along with progress in preimplantation genetic diagnosis, suggests the possibility of screening embryos for traits such as height or cognitive ability. However, the expected outcomes of embryo screening are unclear, which undermines discussion of associated ethical concerns. Here, we use theory, simulations, and real data to evaluate the potential gain of embryo screening, defined as the difference in trait value between the top-scoring embryo and the average embryo. The gain increases very slowly with the number of embryos but more rapidly with the variance explained by the score. Given current technology, the average gain due to screening would be ≈2.5 cm for height and ≈2.5 IQ points for cognitive ability. These mean values are accompanied by wide prediction intervals, and indeed, in large nuclear families, the majority of children top-scoring for height are not the tallest.

Genetic Insights Into Frailty: Association of 9p21-23 Locus With Frailty

Frailty is a complex aging phenotype associated with increased vulnerability to disability and death. Understanding the biological antecedents of frailty may provide clues to healthy aging. The genome-wide association study hotspot, 9p21-23 region, is a risk locus for a number of age-related complex disorders associated with frailty. Hence, we conducted an association study to examine whether variations in 9p21-23 locus plays a role in the pathogenesis of frailty in 637 community-dwelling Ashkenazi Jewish adults aged 65 and older enrolled in the LonGenity study. The strongest association with frailty (adjusted for age and gender) was found with the SNP rs518054 (odds ratio: 1.635, 95% CI = 1.241-2.154; p-value: 4.81 × 10^-04) intergenic and located between LOC105375977 and C9orf146. The prevalence of four SNPs (rs1324192, rs7019262, rs518054, and rs571221) risk alleles haplotype in this region was significantly higher (compared with other haplotypes) in frail older adults compared with non-frail older adults (29.7 vs. 20.8%, p = 0.0005, respectively). Functional analyses using in silico approaches placed rs518054 in the CTCF binding site as well as DNase hypersensitive region. Furthermore, rs518054 was found to be in an enhancer site of NFIB gene located downstream. NFIB is a transcription factor that promotes cell differentiation during development, has antiapoptotic effect, maintains stem cell populations in adult tissues, and also acts as epigenetic regulators. Our study found novel association of SNPs in the regulatory region in the 9p21-23 region with the frailty phenotype; signifying the importance of this locus in aging.

Association of anti-inflammatory cytokine IL10 polymorphisms with motoric cognitive risk syndrome in an Ashkenazi Jewish population

Motoric cognitive risk (MCR) syndrome is a newly described predementia syndrome characterized by the presence of cognitive complaints and slow gait, which is associated with increased risk of conversion to dementia. The underlying biological mechanisms for MCR have not yet been established. Neuroinflammation mediated through cytokines plays a pivotal role in the pathogenesis of dementia. Hence, our objective was to prospectively examine whether variations in cytokine genes (CRP, IFNG, IL1A, IL1B, IL4, IL6, IL10, IL18, TNF, and IL12A) play a role in MCR incidence in 530 community-dwelling Ashkenazi Jewish adults aged 65 years and older without MCR or dementia at baseline enrolled in the LonGenity study. Over a median follow-up of 2.99 years, 70 participants developed MCR. Single nucleotide polymorphisms (SNPs) in the transcriptional regulatory regions of cytokine IL10, rs1800896 (hazard ratio adjusted for age, gender, and education, aHR: 1.667; 95% CI: 1.198-2.321) and rs3024498 (aHR: 1.926; 95% CI: 1.315-2.822), were associated with incident MCR. Functional analysis using in silico approaches indicated associated SNP rs3024498 "C" allele being the local expression quantitative trait locus. Associated alleles of both the SNPs, rs1800896 and rs3024498, were implicated with overexpression of IL10 gene. None of the variants in the neuroinflammatory pathway studied were associated with incident mild cognitive impairment syndrome. These observations support a role for the IL10 gene in dementia pathogenesis by increasing risk of developing MCR in older adults.

Skin collagen fluorophore LW-1 versus skin fluorescence as markers for the long-term progression of subclinical macrovascular disease in type 1 diabetes

BACKGROUND

Skin collagen Long Wavelength Fluorescence (LWF) is widely used as a surrogate marker for accumulation of advanced glycation end-products. Here we determined the relationship of LWF with glycemia, skin fluorescence, and the progression of complications during EDIC in 216 participants from the DCCT.

METHODS

LW-1 and collagen-linked fluorescence (CLF) were measured by either High Performance Liquid Chromatography (HPLC) with fluorescence detection (LW-1) or total fluorescence of collagenase digests (CLF) in insoluble skin collagen extracted from skin biopsies obtained at the end of the DCCT (1993). Skin intrinsic fluorescence (SIF) was noninvasively measured on volar forearm skin at EDIC year 16 by the SCOUT DS instrument.

RESULTS

LW-1 levels significantly increased with age and diabetes duration (P < 0.0001) and significantly decreased by intensive vs. conventional glycemic therapy in both the primary (P < 0.0001) and secondary (P < 0.037) DCCT cohorts. Levels were associated with 13-16 year progression risk of retinopathy (>3 sustained microaneurysms, P = 0.0004) and albumin excretion rate (P = 0.0038), the latter despite adjustment for HbA1c. Comparative analysis for all three fluorescent measures for future risk of subclinical macrovascular disease revealed the following significant (P < 0.05) associations after adjusting for age, diabetes duration and HbA1c: coronary artery calcium with SIF and CLF; intima-media thickness with SIF and LW-1; and left ventricular mass with LW-1 and CLF.

CONCLUSIONS

LW-1 is a novel risk marker that is robustly and independently associated with the future progression of microvascular disease, intima-media thickness and left ventricular mass in type 1 diabetes. Trial registration NCT00360815 and NCT00360893 at clinicaltrials.gov.