Altered hepatic glucose homeostasis in AnxA6-KO mice fed a high-fat diet

PLoS One. 2018 Aug 15;13(8):e0201310. doi: 10.1371/journal.pone.0201310. eCollection 2018.

Abstract

Annexin A6 (AnxA6) controls cholesterol and membrane transport in endo- and exocytosis, and modulates triglyceride accumulation and storage. In addition, AnxA6 acts as a scaffolding protein for negative regulators of growth factor receptors and their effector pathways in many different cell types. Here we investigated the role of AnxA6 in the regulation of whole body lipid metabolism and insulin-regulated glucose homeostasis. Therefore, wildtype (WT) and AnxA6-knockout (KO) mice were fed a high-fat diet (HFD) for 17 weeks. During the course of HFD feeding, AnxA6-KO mice gained less weight compared to controls, which correlated with reduced adiposity. Systemic triglyceride and cholesterol levels of HFD-fed control and AnxA6-KO mice were comparable, with slightly elevated high density lipoprotein (HDL) and reduced triglyceride-rich lipoprotein (TRL) levels in AnxA6-KO mice. AnxA6-KO mice displayed a trend towards improved insulin sensitivity in oral glucose and insulin tolerance tests (OGTT, ITT), which correlated with increased insulin-inducible phosphorylation of protein kinase B (Akt) and ribosomal protein S6 kinase (S6) in liver extracts. However, HFD-fed AnxA6-KO mice failed to downregulate hepatic gluconeogenesis, despite similar insulin levels and insulin signaling activity, as well as expression profiles of insulin-sensitive transcription factors to controls. In addition, increased glycogen storage in livers of HFD- and chow-fed AnxA6-KO animals was observed. Together with an inability to reduce glucose production upon insulin exposure in AnxA6-depleted HuH7 hepatocytes, this implicates AnxA6 contributing to the fine-tuning of hepatic glucose metabolism with potential consequences for the systemic control of glucose in health and disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adiposity / drug effects
  • Animals
  • Annexin A6 / deficiency*
  • Annexin A6 / metabolism
  • Dietary Fats / adverse effects
  • Dietary Fats / pharmacology*
  • Gluconeogenesis / drug effects*
  • Gluconeogenesis / genetics
  • Glucose / genetics
  • Glucose / metabolism*
  • Glycogen / genetics
  • Glycogen / metabolism*
  • Insulin Resistance
  • Lipids / blood
  • Liver / metabolism*
  • Liver / pathology
  • Male
  • Mice
  • Mice, Knockout
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • Ribosomal Protein S6 Kinases / genetics
  • Ribosomal Protein S6 Kinases / metabolism

Substances

  • Annexin A6
  • Anxa6 protein, mouse
  • Dietary Fats
  • Lipids
  • Glycogen
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases
  • Glucose

Grants and funding

T.G. is supported by the University of Sydney (U7007, U7042, U7113, RY253), Sydney, Australia. C.E. is supported by grants from the Ministerio de Economía y Competitividad (BFU2015-66785-P and CSD2009-00016) and Fundació Marató TV3 (PI042182), Spain. C.R. is thankful to CONSOLIDER-INGENIO (MINECO) research program for post-doctoral fellowship [grant number CSD2009-00016] and to Fundació Marató TV3. A.J.H. is supported by a Helen and Robert Ellis Postdoctoral Research fellowship and funding from the Sydney Medical School Foundation, University of Sydney, Australia. A.W.F and A.E. are thankful for support from the German Academic Scholarship Foundation (Studienstiftung des deutschen Volkes).