Abstract 13133: Silencing of Angiopoietin-like Protein 3 (ANGPTL3) in IHH- Hepatocytes Results in Increased Insulin Sensitivity and Reduced Triglyceride-rich VLDL Secretion
AIMS: Homozygosity of loss-of-function mutations in ANGPTL3 -gene results in familial combined hypolipidemia (FHBL2,OMIM #605019) characterized by reduction of all major plasma lipoprotein classes VLDL, LDL, HDL and low circulating free fatty acids, glucose and insulin levels. Thus complete lack of ANGPTL3 in humans not only affects lipid metabolism but also whole-body insulin and glucose balance. Our aim was to investigate the function of ANGPTL3, a hepatic secretory protein, in promoting hypolipidemia and hepatic insulin sensitivity.
METHODS: We used wild type and ANGPTL3-silenced human immortalized hepatocytes (IHH) to investigate the effect of ANGPTL3-silencing on hepatic VLDL secretion and glucose uptake.
RESULTS: We demonstrate that insulin downregulates hepatic secretion of ANGPTL3 and triglyceride-enriched VLDL1-type particles in a dose dependent manner. Similar effect on VLDL secretion was demonstrated with a treatment of PPAR[[Unable to Display Character: ƴ]] agonist rosiglitazone. We further show that ANGPTL3-silenced cells display a more pronounced shift from the secretion of TG-enriched VLDL1-type particles to a secretion of lipid poor VLDL2-type particles during insulin stimulation. Silencing of ANGPTL3 improved hepatic glucose uptake by 20-50 % depending on the glucose and insulin concentration, resulted in a trend towards increased AKT/PKB phosphorylation upon insulin stimulation and downregulated fasting induced transcription factor PGC1α and its downstream targets.
CONCLUSION: Our results indicate a similar function of both insulin and rosiglitazone regarding regulation of ANGPTL3 and VLDL secretion in hepatocytes, and suggest that insulin and PPAR[[Unable to Display Character: ƴ]] might mediate some of their functions via ANGPTL3. Our results give more insight into the liver specific role of ANGPTL3 and links silencing of ANGPTL3 with Insulin sensitivity. Since humans with elevated levels of ANGPTL3 display hyperlipidemia and insulin resistance it might be beneficial to target ANGPTL3 silencing in the liver, the major site of ANGPTL3 expression, to balance lipid and glucose homeostasis and lower risk for cardiovascular diseases.
Author Disclosures: A.M. Tikka: None. P. Laurila: None. J. Soronen: None. J. Metso: None. C. Ehnholm: None. M. Jauhiainen: None.
- © 2014 by American Heart Association, Inc.