IL6R and obesity due to melanocortin 4 receptor deficiency: Overall, Mendelian randomization experiments including gene variants in inflammation pathways did not evidence a causal role of inflammation in obesity or type 2 diabetes (Brunner et al., 2008; Rafiq et al., 2008; Welsh et al., 2010) and conflicting results about a causal link between inflammation and cardiovascular disease have been reported (Brunner et al., 2008; The Interleukin-6 Receptor Mendelian Randomisation Analysis (IL6R MR) Consortium, 2012; Raman et al., 2013; Varbo et al., 2013).