Prevalence of multiple sclerosis varies with geographic latitude. We hypothesized that this fact might be partially associated with the influence of latitude on circadian rhythm and consequently that genetic variability of key circadian rhythm regulators, ARNTL and CLOCK genes, might contribute to the risk for multiple sclerosis. Our aim was to analyse selected polymorphisms of ARNTL and CLOCK, and their association with multiple sclerosis. A total of 900 Caucasian patients and 1024 healthy controls were compared for genetic signature at 8 SNPs, 4 for each of both genes. We found a statistically significant difference in genotype (ARNTL rs3789327, P = 7.5·10−5; CLOCK rs6811520 P = 0.02) distributions in patients and controls. The ARNTL rs3789327 CC genotype was associated with higher risk for multiple sclerosis at an OR of 1.67 (95% CI 1.35–2.07, P = 0.0001) and the CLOCK rs6811520 genotype CC at an OR of 1.40 (95% CI 1.13–1.73, P = 0.002). The results of this study suggest that genetic variability in the ARNTL and CLOCK genes might be associated with risk for multiple sclerosis.

We confirmed high prevalence of pain, affecting approximately more than half of patients during the course of MS. Pain in MS is associated with disability, depression and, especially with anxiety, which has significant implications for treatment.

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Background. Previous studies have shown impaired fibrinolysis in multiple sclerosis (MS) and implicated extracellular proteolytic enzymes as important factors in demyelinating neuroinflammatory disorders. Tissue-type plasminogen activator (t-PA) and its inhibitor (PAI-1) are key molecules in both fibrinolysis and extracellular proteolysis. In the present study, an association of the TPA Alu I/D and PAI-1 4G/5G polymorphisms with MS was analyzed within the Genomic Network for Multiple Sclerosis (GENoMS). Methods. The GENoMS includes four populations (Croatian, Slovenian, Serbian, and Bosnian and Herzegovinian) sharing the same geographic location and a similar ethnic background. A total of 885 patients and 656 ethnically matched healthy blood donors with no history of MS in their families were genotyped using PCR-RFLP. Results. TPA DD homozygosity was protective (OR = 0.79, 95% CI 0.63–0.99, P = 0.037) and PAI 5G5G was a risk factor for MS (OR = 1.30, 95% CI 1.01–1.66, P = 0.038). A significant effect of the genotype/carrier combination was detected in 5G5G/I carriers (OR = 1.39 95% CI 1.06–1.82, P = 0.017). Conclusions. We found a significantly harmful effect of the combination of the PAI-1 5G/5G genotype and TPA I allele on MS susceptibility, which indicates the importance of gene-gene interactions in complex diseases such as MS.