title: 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.
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.
authors.affiliation: *National Institute for Health and Welfare, Public Health Genomics Unit, Biomedicum, Helsinki, Finland.
authors.forename: Anna
authors.initials: A
authors.lastname: Tikka
authors.affiliation: *National Institute for Health and Welfare, Public Health Genomics Unit, Biomedicum, Helsinki, Finland.
authors.forename: Jarkko
authors.initials: J
authors.lastname: Soronen
authors.affiliation: *National Institute for Health and Welfare, Public Health Genomics Unit, Biomedicum, Helsinki, Finland.
authors.forename: Pirkka-Pekka
authors.initials: PP
authors.lastname: Laurila
authors.affiliation: *National Institute for Health and Welfare, Public Health Genomics Unit, Biomedicum, Helsinki, Finland.
authors.forename: Jari
authors.initials: J
authors.lastname: Metso
authors.affiliation: *National Institute for Health and Welfare, Public Health Genomics Unit, Biomedicum, Helsinki, Finland.
authors.forename: Christian
authors.initials: C
authors.lastname: Ehnholm
authors.affiliation: *National Institute for Health and Welfare, Public Health Genomics Unit, Biomedicum, Helsinki, Finland.
authors.forename: Matti
authors.initials: M
authors.lastname: Jauhiainen
mesh_terms: D042683:Angiopoietin-1 / Q000235:genetics* / Q000378:metabolism; D002461:Cell Line, Transformed; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D005227:Fatty Acids / Q000378:metabolism / Q000493:pharmacokinetics; D015870:Gene Expression; D005943:Gluconeogenesis / Q000235:genetics*; D005947:Glucose / Q000378:metabolism / Q000493:pharmacokinetics; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D008079:Lipoproteins, VLDL / Q000378:metabolism*; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077154:Rosiglitazone; D045162:Thiazolidinediones / Q000494:pharmacology; D014280:Triglycerides / Q000378:metabolism*
chemical_list: C467630:ANGPT1 protein, human; D042683:Angiopoietin-1; D005227:Fatty Acids; D007004:Hypoglycemic Agents; D007328:Insulin; D008079:Lipoproteins, VLDL; D045162:Thiazolidinediones; D014280:Triglycerides; C030106:very low density lipoprotein triglyceride; D000077154:Rosiglitazone; D005947:Glucose