TLR4 and myocardial infarction: These results were correlated with the suppression of the mRNA level of TLR4 in the cardiac tissue and the diminution of the protein level of MyD88, which were elevated in the myocardium following isoproterenol-induced MI.13 This finding of AMPK activation by metformin and the subsequent inhibition of TLR4 expression and activity led to the hypothesis that there may be a link between AMPK and TLRs.