INS and Insulin resistance: Previous research has already revealed associations between insulin levels and methylation of the mitochondrial transcription factor A (TFAM) (r = -0.49, p < 0.04; Sookoian et al., 2010), and between insulin resistance and mtDNA methylation (4.6-fold higher in insulin-resistant vs. insulin-sensitive subjects, p < 0.05; Zheng et al., 2015), which is indicative for an epigenetic link between both factors in adults.