IRS1 and Insulin resistance: Activated mTORC1/S6K1 phosphorylates inhibitory serine residues of IRS-1 (Ser612)(39) hindering signalling downstream.(1,15) Many of the preceding studies have either focused on the effect of the BCAA at the whole body level,(40–42) or did not study BCKA, so the significance of KIC and the other BCKA in mediating muscle insulin resistance was not clear.