title: Joint analysis of individual participants' data from 17 studies on the association of the IL6 variant -174G>C with circulating glucose levels, interleukin-6 levels, and body mass index.
abstract: BACKGROUND
  Several studies have investigated associations between the -174G>C single nucleotide polymorphism (rs1800795) of the IL6 gene and phenotypes related to type 2 diabetes mellitus (T2DM) but presented inconsistent results.
  
  
  OBJECTIVE
  This joint analysis aimed to clarify whether IL6 -174G>C was associated with glucose and circulating interleukin-6 concentrations as well as body mass index (BMI).
  
  
  METHODS
  Individual-level data from all studies of the IL6-T2DM consortium on Caucasian subjects with available BMI were collected. As study-specific estimates did not show heterogeneity (P>0.1), they were combined by using the inverse-variance fixed-effect model.
  
  
  RESULTS
  The main analysis included 9440, 7398, 24,117, or 5659 non-diabetic and manifest T2DM subjects for fasting glucose, 2-hour glucose, BMI, or circulating interleukin-6 levels, respectively. IL6 -174 C-allele carriers had significantly lower fasting glucose (-0.091 mmol/L, P=0.014). There was no evidence for association between IL6 -174G>C and BMI or interleukin-6 levels, except in some subgroups.
  
  
  CONCLUSIONS
  Our data suggest that C-allele carriers of the IL6 -174G>C polymorphism have lower fasting glucose levels on average, which substantiates previous findings of decreased T2DM risk of these subjects.
authors.affiliation: Institute of Epidemiology, Helmholtz Zentrum Munchen, Neuherberg, Germany.
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