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Abstract Disclosure: A. Gattu: None. M. Tanzer: None. T. Yaron: None. L. Cantley: None. C.R. Kahn: None. Hepatic insulin resistance is central to type 2 diabetes (T2D). Understanding the cellular drivers underlying insulin resistance in the liver is challenging since, in vivo, this can be due to cell-intrinsic defects in insulin signaling, as well as the effects of multiple circulating factors that can modify insulin signaling. Here, we have utilized inducible pluripotent stem cells (iPS) from 8 control and 8 T2D patients differentiated in vitro into hepatocytes (iHeps) to dissect the cell-intrinsic defects in hepatic insulin resistance. We find that following stimulation with insulin, T2D iHeps displayed “pathway-selective insulin resistance,” in which insulin failed to suppress gene expression of critical gluconeogenic enzymes (PCK1, G6PC) but continued to stimulate expression of the lipogenic enzymes (FASN, ACACA). This was associated with a 1.5-fold higher level of insulin stimulation of C14 acetate into lipids, i.e., de novo lipogenesis. Immunoblotting analysis showed T2D iHeps exhibited a 50% reduction in phosphorylation of the insulin receptor IRY1135 and ∼ 30% reductions in AKTT308, GSK3αS21/GSK3βS9, and FOXO1T24/FOXO3aT32 in T2D following insulin stimulation for 10 minutes. To define the full spectrum of alterations in signaling in iHeps, we used unbiased LC-MS/MS-based phosphoproteomics. This revealed alterations in 987 insulin-regulated phosphosphorylations that had increased phosphorylation after insulin treatment and alterations in 723 sites for which insulin decreased phosphorylation (with a |fold-change| 1.5 and adj. p 0.05). These alterations were of two types: 43% of the altered insulin-regulated phosphosites showed reduced or “impaired” insulin regulation, but 57% of the phosphosites displayed new or significantly increased insulin-regulated phosphorylations in T2D, i.e., “emergent” signaling. The impaired signaling in T2D included losses in the insulin receptor signaling cascade, Rho-GTPase pathway, Notch-HLH, and anti-viral mechanisms of IFN-stimulated genes. In contrast, emergent signaling included other components of the Rho-GTPase pathway, metabolism of RNA, membrane trafficking, and chromatin-modifying enzymes. Using an AI-based kinase-substrate association analysis, we found that the deficiencies in signaling represented reduced actions of kinases AKT2, AKT3, PKCθ, CHK2, PHKG2, and/or STK32C kinases, while the emergent changes represented increases in ROCK1, ROCK2, MST4 and/or BCKDK kinase activity. In summary, phosphoproteomic analyses of iHeps revealed a comprehensive insulin signaling network disrupted in insulin resistance in the liver in T2D, which underlies the etiology of insulin resistance. These alterations can be ascribed to changes in the activity of two classes of upstream kinases, representing potential new targets for treating T2D. Presentation: 6/1/2024
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