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Dysregulation in the circadian system induced by variants of clock genes has been associated with type 2 diabetes. Evidence for the role of cryptochromes, core components of the system, in regulating glucose homeostasis is not supported by CRY1 candidate gene association studies for diabetes and insulin resistance in human, suggesting possible dietary influences. The purpose of this study was to test for interactions between a CRY1 polymorphism, rs2287161, and carbohydrate intake on insulin resistance in two independent populations: a Mediterranean ( n = 728) and an European origin North American population ( n = 820). Linear regression interaction models were performed in two populations to test for gene-diet interactions on fasting insulin and glucose and two insulin-related traits, homeostasis model assessment of insulin resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI). In addition, fixed effects meta-analyses for these interactions were performed. Cohort-specific interaction analyses showed significant interactions between the CRY1 variant and dietary carbohydrates for insulin resistance in both populations ( p < 0.05). Findings from the meta-analyses of carbohydrate-single nucleotide polymorphism interactions indicated that an increase in carbohydrate intake (% of energy intake) was associated with a significant increase in HOMA-IR ( p = 0.011), fasting insulin ( p = 0.007) and a decrease in QUICKI ( p = 0.028), only among individuals homozygous for the minor C allele. This novel finding supports the link between the circadian system and glucose metabolism and suggests the importance this CRY1 locus in developing personalized nutrition programs aimed at reducing insulin resistance and diabetes risk. [ABSTRACT FROM AUTHOR]

Sunlight exposure has been shown to alter DNA methylation patterns across several human cell-types, including T-lymphocytes. Since epigenetic changes establish gene expression profiles, changes in DNA methylation induced by sunlight exposure warrant investigation. The purpose of this study was to assess the effects of sunlight exposure on CD4+ T-cell methylation patterns on an epigenome-wide scale in a North American population of European origin (n=991). In addition, we investigated the genetic contribution to epigenetic variation (methylQTL). We used linear regression to test the associations between methylation scores at 461,281 cytosine-phosphate-guanine (CpG) sites and sunlight exposure, followed by a genome-wide association analysis (methylQTL) to test for associations between methylation at the top CpG locus and common genetic variants, assuming an additive genetic model. We observed an epigenome-wide significant association between sunlight exposure and methylation status at cg26930596 (p=9.2×10(-8)), a CpG site located in protein kinase C zeta (PRKCZ), a gene previously shown to be entrained by light. MethylQTL analysis resulted in significant associations between cg26930596 and two intergenic single nucleotide polymorphisms on chromosome 3, rs4574216 (p=1.5×10(-10)) and rs4405858 (p=1.9×10(-9)). These common genetic variants reside downstream of WWTR1, a transcriptional co-activator of PRKCZ. Associations observed in the North American population, however, did not replicate in an independent Mediterranean cohort. Our preliminary results support the role of sunlight exposure in epigenetic processes, and lay the groundwork for future studies of the molecular link between sunlight and physiologic processes such as tumorigenesis and metabolism.

Scope: Despite the solid connection between REV-ERB and obesity, the information about whether genetic variations at this locus may be associated with obesity traits is scarce. Therefore our objective was to study the association between REV-ERB-ALPHA1 rs2314339 and obesity in two independent populations., Methods and Results: Participants were 2214 subjects from Spanish Mediterranean (n = 1404) and North American (n = 810) populations. Anthropometric, biochemical, dietary, and genotype analyses were performed. We found novel associations between the REV-ERB-ALPHA1 rs2314339 genotype and obesity in two independent populations: in Spanish Mediterranean and North American groups, the frequency of the minor-allele-carriers (AA+ AG) was significantly lower in the "abdominally obese" group than in those of the "nonabdominally obese" group (p < 0.05). Minor allele carriers had lower probability of abdominal obesity than noncarriers, and the effect was of similar magnitude for both populations (OR ≈ 1.50). There were consistent associations between REV-ERB-ALPHA1 genotype and obesity-related traits (p < 0.05). Energy intake was not significantly associated with REV-ERB-ALPHA1 rs2314339. However, physical activity significantly differed by genotype. A significant interaction between the REV-ERB-ALPHA1 variant and monounsaturated-fatty-acids (MUFA) intake for obesity was also detected in the Mediterranean population., Conclusion: This new discovery highlights the importance of REV-ERB-ALPHA1 in obesity and provides evidence for the connection between our biological clock and obesity-related traits., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)