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Hindrik Mulder

Hindrik Mulder

Principal investigator

Hindrik Mulder

Glucagon-Like Peptide 1 Stimulates Insulin Secretion via Inhibiting RhoA/ROCK Signaling and Disassembling Glucotoxicity-Induced Stress Fibers

Author

  • Xiangchen Kong
  • Dan Yan
  • Jiangming Sun
  • Xuerui Wu
  • Hindrik Mulder
  • Xianxin Hua
  • Xiaosong Ma

Summary, in English

Chronic hyperglycemia leads to pancreatic beta-cell dysfunction characterized by diminished glucose-stimulated insulin secretion (GSIS), but the precise cellular processes involved are largely unknown. Here we show that pancreatic beta-cells chronically exposed to a high glucose level displayed substantially increased amounts of stress fibers compared with beta-cells cultured at a low glucose level. beta-Cells at high glucose were refractory to glucose-induced actin cytoskeleton remodeling and insulin secretion. Importantly, F-actin depolymerization by either cytochalasin B or latrunculin B restored glucotoxicity-diminished GSIS. The effects of glucotoxicity on increasing stress fibers and reducing GSIS were reversed by Y-27632, a Rho-associated kinase (ROCK)-specific inhibitor, which caused actin depolymerization and enhanced GSIS. Notably, glucagon-like peptide-1-(7-36) amide (GLP-1), a peptide hormone that stimulates GSIS at both normal and hyperglycemic conditions, also reversed glucotoxicity-induced increase of stress fibers and reduction of GSIS. In addition, GLP-1 inhibited glucotoxicity-induced activation of RhoA/ROCK and thereby resulted in actin depolymerization and potentiation of GSIS. Furthermore, this effect of GLP-1 was mimicked by cAMP-increasing agents forskolin and 3-isobutyl-1-methylxanthine as well as the protein kinase A agonist 6-Bnz-cAMP-AM whereas it was abolished by the protein kinase A inhibitor Rp-Adenosine 3',5'-cyclic monophosphorothioate triethylammonium salt. To establish a clinical relevance of our findings, we examined the association of genetic variants of RhoA/ROCK with metabolic traits in homeostasis model assessment index of insulin resistance. Several single-nucleotide polymorphisms in and around RHOA were associated with elevated fasting insulin and homeostasis model assessment index of insulin resistance, suggesting a possible role in metabolic dysregulation. Collectively these findings unravel a novel mechanism whereby GLP-1 potentiates glucotoxicity-diminished GSIS by depolymerizing F-actin cytoskeleton via protein kinase A-mediated inhibition of the RhoA-ROCK signaling pathway.

Department/s

  • Diabetes - Molecular Metabolism
  • EXODIAB: Excellence of Diabetes Research in Sweden

Publishing year

2014

Language

English

Pages

4676-4685

Publication/Series

Endocrinology

Volume

155

Issue

12

Document type

Journal article

Publisher

Oxford University Press

Topic

  • Endocrinology and Diabetes

Status

Published

Research group

  • Diabetes - Molecular Metabolism

ISBN/ISSN/Other

  • ISSN: 0013-7227