Muscle-Derived Angiopoietin-Like Protein 4 Is Induced by Fatty Acids via Peroxisome Proliferator–Activated Receptor (PPAR)-δ and Is of Metabolic Relevance in Humans

Abstract

OBJECTIVE— Long-chain fatty acids (LCFAs) contribute to metabolic homeostasis in part via gene regulation. This study's objective was to identify novel LCFA target genes in human skeletal muscle cells (myotubes). RESEARCH DESIGN AND METHODS— In vitro methods included culture and treatment of human myotubes and C2C12 cells, gene array analysis, real-time RT-PCR, Western blotting, ELISA, chromatin immunoprecipitation, and RNA interference. Human subjects (two cohorts) were characterized by oral glucose tolerance test, hyperinsulinemic-euglycemic clamp, magnetic resonance imaging and spectroscopy, and standard blood analyses (glucose, insulin, C-peptide, and plasma lipids). RESULTS— We show here that ANGPTL4 (encoding angiopoietin-like protein 4) represents a prominent LCFA-responsive gene in human myotubes. LCFA activated peroxisome proliferator-activated receptor (PPAR)-δ, but not PPAR-α or -γ, and pharmacological activation of PPAR-δ markedly induced ANGPTL4 production and secretion. In C2C12 myocytes, knockdown of PPARD , but not of PPARG , blocked LCFA-mediated ANGPTL4 induction, and LCFA treatment resulted in PPAR-δ recruitment to the ANGPTL4 gene. In addition, pharmacological PPAR-δ activation induced LIPE (encoding hormone-sensitive lipase), and this response crucially depended on ANGPTL4, as revealed by ANGPTL4 knockdown. In a human cohort of 108 thoroughly phenotyped subjects, plasma ANGPTL4 positively correlated with fasting nonesterified fatty acids ( P = 0.0036) and adipose tissue lipolysis ( P = 0.0012). Moreover, in 38 myotube donors, plasma ANGPTL4 levels and adipose tissue lipolysis in vivo were reflected by basal myotube ANGPTL4 expression in vitro ( P = 0.02, both). CONCLUSIONS— ANGPTL4 is produced by human myotubes in response to LCFA via PPAR-δ, and muscle-derived ANGPTL4 seems to be of systemic relevance in humans.

Quantitation of serum angiopoietin-like proteins 3 and 4 in a Finnish population sample

“…There are several basic residue-rich regions in ANGPTL 3 and 4, both in N-and C-terminal regions that could mediate the binding of these proteins at the sites important for LPL activity. For ANGPTL3, good agreement with previous reports showing that ANGPTL3 is present in the circulation at a higher concentration (224 ng/ml) compared with ANGPTL4 (1.73 ng/ ml) ( 22,23 ). Although some differences exist in the values reported for ANGPTL 3 and 4, these probably are due to differences in method standardization, population samples, and/or the antibodies used.…”

Down-regulation of SREBP-1c is associated with the development of burned-out NASH

“…4B and 7). Consistent with the immunoblot results were no meaningful differences in the mRNA levels of the PPAR target genes CPT1, MCAD, AOX and FABP1 [22][23][24][25], the PPAR/ target genes pyruvate dehydrogenase kinase (PDK) 4 and angiopoietin-like protein 4 (ANGPTL4) [26,27], or the PPAR target genes FABP4 and fat-specific protein 27 (FSP27) [28,29] among the groups ( Fig. 2 and Supplementary Fig.…”

Microbiota regulate intestinal epithelial gene expression by suppressing the transcription factor Hepatocyte nuclear factor 4 alpha

“…Though hnf4a mutant zebrafish have reduced in3.4 activity in the intestinal epithelium based on transgenic reporter assays, the transcript levels of the endogenous zebrafish angptl4 gene appears unaffected in both larval digestive tracts and adult IECs. The zebrafish genome encodes two additional HNF4 family members (hnf4b, hnf4g), and previous studies in mammals have shown Angptl4 can be regulated by other metabolically activated nuclear receptors (Staiger et al 2009;Korecka et al 2013). We hypothesize that loss of HNF4A function may lead to a metabolic imbalance leading to atypical or compensatory activation of other trans-and cis-factors that control expression of angptl4 and other genes in the intestine.…”