Evidence coupling increased hexosamine biosynthesis pathway activity to membrane cholesterol toxicity and cortical filamentous actin derangement contributing to cellular insulin resistance

Padma Bhonagiri, Guruprasad R. Pattar, Kirk M. Habegger, Alicia M. McCarthy, Lixuan Tackett, Jeffrey S. Elmendorf

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Hyper Insulinemia is known to promote the progression/worsening of insulin resistance. Evidence reveals a hidden cost of hyperinsulinemia on plasma membrane (PM) phosphatidylinositol 4,5-bisphosphate (PIP2)-regulated filamentous actin (F-actin) structure, components critical to the normal operation of the insulin-regulated glucose transport System. Here we delineated whether increased glucose flux through the hexosamine biosynthesis pathway (HBP) causes PIP2/F-actin dysregulation and subsequent insulin resistance. Increased glycosylation events were detected in 3T3-L1 adipocytes cultured under conditions closely resembling physiological hyperinsulinemia (5 nM insulin; 12 h) and in cells in which HBP activity was amplified by 2 mM glucosamine (GlcN). Both the physiological hyperinsulinemia and experimental GlcN challenge induced comparable losses of PIP2 and F-actin. In addition to protecting against the insulin-induced membrane/cytoskeletal abnormality and insulin-resistant state, exogenous PIP2 corrected the GlcN-induced insult on these parameters. Moreover, in accordance with HBP flux directly weakening PIP2/F-actin structure, pharmacological inhibition of the rate-limiting HBP enzyme [glutamine-fructose-6-phosphate amidotransferase (GFAT)] restored PIP2-regulated F-actin structure and insulin responsiveness. Conversely, overexpression of GFAT was associated with a loss of detectable PM PIP2 and insulin sensitivity. Even less invasive challenges with glucose, in the absence of insulin, also led to PIP2/F-actin dysregulation. Mechanistically we found that increased HBP activity increased PM cholesterol, the removal of which normalized PIP 2/F-actin levels. Accordingly, these data suggest that glucose transporter-4 functionality, dependent on PIP2 and/or F-actin status, can be critically compromised by inappropriate HBP activity. Furthermore, these data are consistent with the PM cholesterol accrual/toxicity as a mechanistic basis of the HBP-induced defects in PIP2/F-actin structure and impaired glucose transporter-4 regulation.

Original languageEnglish (US)
Pages (from-to)3373-3384
Number of pages12
JournalEndocrinology
Volume152
Issue number9
DOIs
StatePublished - Sep 1 2011

ASJC Scopus subject areas

  • Endocrinology

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