title: Functional characterization of TLR4 +3725 G/C polymorphism and association with protection against overweight.
abstract: Subclinical low-grade systemic inflammation has been associated with obesity, insulin resistance and metabolic syndrome (MS). Recent studies have highlighted the role of gut microbiota in these disorders. The toll-like receptor 4 (TLR4) plays a key role in the innate immune response activation. We studied two polymorphisms (+3725G/C and 11350G/C) in the 3' untranslated region (3'UTR) of the TLR4 gene that may alter its expression and their association with metabolic disorders related to systemic inflammation. We cloned the 3'UTR into a luciferase reporter system and compared wild-type 3'UTR (WT) and +3725C variant (MUT) constructs luciferase activities. MUT construct reduced the reporter gene activity by 30% compared to WT (P = 0.0001). To evaluate the association between these polymorphisms with biochemical and clinical overweight related variables, we conducted a population cross-sectional study in 966 men of Argentine general population. Considering smoking as a confounding variable that causes systemic inflammation, we studied these possible effects in both, smokers and nonsmokers. The 11350G/C polymorphism was not detected in our sample whereas the CC genotype of +3725 polymorphism was associated with lean subjects (p = 0.011) and higher Adiponectin levels (p = 0.021). Subjects without any NCEP/ATP III MS component were associated with this genotype as well (p = 0.001). These results were strengthened in nonsmokers, in which CC genotype was associated with lean subjects (p = 0.003) and compared with G carriers showed significantly lower BMI (25.53 vs. 28.60 kg/m2; p = 0.023) and waist circumference (89.27 vs. 97.51 cm; p = 0.025). None of these associations were found in smokers. These results showed that +3725C variant has a functional effect down-regulating gene expression and it could be considered as a predictive factor against overweight, particularly in nonsmokers. Considering the role of TLR4 in inflammation, these findings would suggest that the presence of +3725C variant could predict a lower prevalence of chronic metabolic disorders.
authors.affiliation: Instituto de Estudios de la Inmunidad Humoral (IDEHU), CONICET-UBA-Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina. pufetin@gmail.com
authors.forename: Alberto
authors.initials: A
authors.lastname: Penas-Steinhardt
authors.forename: Lucía Soledad
authors.initials: LS
authors.lastname: Barcos
authors.forename: Fiorella Sabrina
authors.initials: FS
authors.lastname: Belforte
authors.forename: Martha
authors.initials: M
authors.lastname: de Sereday
authors.forename: Jorge
authors.initials: J
authors.lastname: Vilariño
authors.forename: Claudio Daniel
authors.initials: CD
authors.lastname: Gonzalez
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Martínez-Larrad
authors.forename: Mariana Lorena
authors.initials: ML
authors.lastname: Tellechea
authors.forename: Manuel
authors.initials: M
authors.lastname: Serrano-Ríos
authors.forename: Edgardo
authors.initials: E
authors.lastname: Poskus
authors.forename: Gustavo Daniel
authors.initials: GD
authors.lastname: Frechtel
authors.forename: Federico Coluccio
authors.initials: FC
authors.lastname: Leskow
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D052242:Adiponectin / Q000097:blood; D000328:Adult; D005786:Gene Expression Regulation; D056726:Genetic Association Studies; D006801:Humans; D007113:Immunity, Innate; D007333:Insulin Resistance / Q000235:genetics; D008297:Male; D024821:Metabolic Syndrome / Q000235:genetics; D009765:Obesity / Q000235:genetics; D050177:Overweight / Q000097:blood / Q000453:epidemiology / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D012907:Smoking; D051197:Toll-Like Receptor 4 / Q000235:genetics*
chemical_list: D020413:3' Untranslated Regions; D052242:Adiponectin; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4