Silencing of ANGPTL 3 (angiopoietin-like protein 3) in human hepatocytes results in decreased expression of gluconeogenic genes and reduced triacylglycerol-rich VLDL secretion upon insulin stimulation

Biosci Rep. 2014 Dec 12;34(6):e00160. doi: 10.1042/BSR20140115.

Abstract

Homozygosity of loss-of-function mutations in ANGPTL3 (angiopoietin-like protein 3)-gene results in FHBL2 (familial combined hypolipidaemia, OMIM #605019) characterized by the reduction of all major plasma lipoprotein classes, which includes VLDL (very-low-density lipoprotein), LDL (low-density lipoprotein), HDL (high-density lipoprotein) and low circulating NEFAs (non-esterified fatty acids), glucose and insulin levels. Thus complete lack of ANGPTL3 in humans not only affects lipid metabolism, but also affects whole-body insulin and glucose balance. We used wild-type and ANGPTL3-silenced IHHs (human immortalized hepatocytes) to investigate the effect of ANGPTL3 silencing on hepatocyte-specific VLDL secretion and glucose uptake. We demonstrate that both insulin and PPARγ (peroxisome-proliferator-activated receptor γ) agonist rosiglitazone down-regulate the secretion of ANGPTL3 and TAG (triacylglycerol)-enriched VLDL1-type particles in a dose-dependent manner. Silencing of ANGPTL3 improved glucose uptake in hepatocytes by 20-50% and influenced down-regulation of gluconeogenic genes, suggesting that silencing of ANGPTL3 improves insulin sensitivity. We further show that ANGPTL3-silenced cells display a more pronounced shift from the secretion of TAG-enriched VLDL1-type particles to secretion of lipid poor VLDL2-type particles during insulin stimulation. These data suggest liver-specific mechanisms involved in the reported insulin-sensitive phenotype of ANGPTL3-deficient humans, featuring lower plasma insulin and glucose levels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angiopoietin-1 / genetics*
  • Angiopoietin-1 / metabolism
  • Cell Line, Transformed
  • Dose-Response Relationship, Drug
  • Enzyme-Linked Immunosorbent Assay
  • Fatty Acids / metabolism
  • Fatty Acids / pharmacokinetics
  • Gene Expression
  • Gluconeogenesis / genetics*
  • Glucose / metabolism
  • Glucose / pharmacokinetics
  • Hepatocytes / cytology
  • Hepatocytes / drug effects*
  • Hepatocytes / metabolism
  • Humans
  • Hypoglycemic Agents / pharmacology
  • Insulin / pharmacology*
  • Lipoproteins, VLDL / metabolism*
  • RNA Interference*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Rosiglitazone
  • Thiazolidinediones / pharmacology
  • Triglycerides / metabolism*

Substances

  • ANGPT1 protein, human
  • Angiopoietin-1
  • Fatty Acids
  • Hypoglycemic Agents
  • Insulin
  • Lipoproteins, VLDL
  • Thiazolidinediones
  • Triglycerides
  • very low density lipoprotein triglyceride
  • Rosiglitazone
  • Glucose