Direct Hepatocyte Insulin Signaling Is Required for Lipogenesis but Is Dispensable for the Suppression of Glucose Production.

TitleDirect Hepatocyte Insulin Signaling Is Required for Lipogenesis but Is Dispensable for the Suppression of Glucose Production.
Publication TypeJournal Article
Year of Publication2016
AuthorsTitchenell, PM, Quinn, WJ, Lu, M, Chu, Q, Lu, W, Li, C, Chen, H, Monks, BR, Chen, J, Rabinowitz, JD, Birnbaum, MJ
JournalCell Metab
Volume23
Issue6
Pagination1154-1166
Date Published2016 Jun 14
ISSN1932-7420
KeywordsAdipose Tissue, Animals, Diet, Efferent Pathways, Fatty Acids, Nonesterified, Forkhead Box Protein O1, Gene Deletion, Gene Expression Regulation, Glucagon, Glucokinase, Gluconeogenesis, Glucose, Glucose Tolerance Test, Heparin, Hepatocytes, Insulin, Insulin Resistance, Lipogenesis, Liver, Male, Mechanistic Target of Rapamycin Complex 1, Mice, Knockout, Multiprotein Complexes, Postprandial Period, Proto-Oncogene Proteins c-akt, Signal Transduction, TOR Serine-Threonine Kinases, Vagus Nerve
Abstract

<p>During insulin-resistant states such as type II diabetes mellitus (T2DM), insulin fails to suppress hepatic glucose production (HGP) yet promotes lipid synthesis. This metabolic state has been termed "selective insulin resistance" to indicate a defect in one arm of the insulin-signaling cascade, potentially downstream of Akt. Here we demonstrate that Akt-dependent activation of mTORC1 and inhibition of Foxo1 are required and sufficient for de novo lipogenesis, suggesting that hepatic insulin signaling is likely to be intact in insulin-resistant states. Moreover, cell-nonautonomous suppression of HGP by insulin depends on a reduction of adipocyte lipolysis and serum FFAs but is independent of vagal efferents or glucagon signaling. These data are consistent with a model in which, during T2DM, intact liver insulin signaling drives enhanced lipogenesis while excess circulating FFAs become a dominant inducer of nonsuppressible HGP.</p>

DOI10.1016/j.cmet.2016.04.022
Alternate JournalCell Metab
PubMed ID27238637
PubMed Central IDPMC4909537
Grant ListF32 DK101175 / DK / NIDDK NIH HHS / United States
P30 DK019525 / DK / NIDDK NIH HHS / United States
R01 DK056886 / DK / NIDDK NIH HHS / United States